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Oracle - SQL - Unique Constraint
 
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Oracle - SQL - Unique Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
UNIQUE KEY CONSTRAINT IN ORACLE SQL WITH EXAMPLE
 
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This is a free video tutorial by Kishan mashru on unique constraint in Oracle SQL, the video firstly explains what unique constraint is and how it can be used along with its various limitations, then the video gives perfect examples to understand how to create a unique key at the column level or inline, or at the table level i.e out of line. The video gives a demonstration on ALTER TABLE ADD CONSTRAINT and ALTER TABLE DROP CONSTRAINT statements also.
Views: 1050 Kishan Mashru
Oracle SQL Tutorial 13 - How to Add Column Constraints (Attributes)
 
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So far, we have this table declaration: CREATE TABLE users( user_id NUMBER, username VARCHAR(50 CHAR) first_name VARCHAR2(50 CHAR), last_name VARCHAR2(50 CHAR) ) We can run this command see that it works. As we are learning though, we are going to want to be able to recreate our table with different settings and such, but if you try to run this command, it will complain that the table already exists. So we first need to delete this table before we start editing settings. When we get more experienced, we will learn about ways to edit the structure of a table that already exists. To fix this, we can get rid of the table using the DROP TABLE command: DROP TABLE users You can run this every time if you need to practice by adding a semicolon after it. This is how you can tell Oracle that you are putting in another command after it. This is known as a delimiter. When you run the script, it is going to run both commands. Now we can go through and reconsider our table structure. This is fine for starting out because we don't have any important data in our database, but once your database is in production you are not going to want to just drop tables. In the last video we discussed different constraints that you can apply to columns in a database table, but how do you actually apply these when you are creating a table? The first way you define constraints is to put them right after the column in your CREATE TABLE statement. CREATE TABLE users( username VARCHAR2(50 CHAR) NOT NULL ) When we define constraints this way, we usually say we are adding column attributes. If you have two constraints you want to add, you just put one after the other with spaces in between. There is no particular order that is required. CREATE TABLE users( username VARCHAR2(50 CHAR) NOT NULL UNIQUE ) In this situation we have already given the column the NOT NULL and UNIQUE attributes, so we should consider making this a primary key: CREATE TABLE users( username VARCHAR2(50 CHAR) PRIMARY KEY ) As you can see, adding column attributes is super easy. We can add a default like this: CREATE TABLE users( username VARCHAR2(50 CHAR) PRIMARY KEY, account_balance NUMBER DEFAULT 0 ) Note that now we need the comma after the first row. There are a few constraints we did not talk go through an example, specifically foreign keys and check constraints. We will be adding these constraints to our database in future videos. In the mean time, I have a thought for you… Many people prefer to name their column constraints. That way, we can refer to certain constraints by name. For example, we might have a primary key constraint that could be named users_pk. The way we are creating these constraints does not allow for this feature, so in the next video we are going to be discussing different ways to create constraints. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 21270 Caleb Curry
44. Unique Constraint in Oracle
 
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In this video you will learn about Unique Constraint in Oracle. The UNIQUE constraint uniquely identifies each record in a database table. The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it. Note that you can have many UNIQUE constraints per table, but only one PRIMARY KEY constraint per table. For Support =========== Email: [email protected] Contact Form: http://www.learninhindi.com/home/contact Our Social Media ================ Facebook: https://www.facebook.com/LearnInHindi Twitter: https://twitter.com/LearnInHindi For Training & Videos ===================== For more videos and articles visit: http://www.learninhindi.com Free Java Programming In Hindi Course ===================================== https://www.youtube.com/playlist?list=PLOZ3jentlCDAwwhMyoLISrxkXTADGp7PH Free Oracle PL/SQL Programming In Hindi Course ============================================== https://www.youtube.com/playlist?list=PLB5DA82419C2D99B6 Free C Programming In Hindi Course ================================== https://www.youtube.com/playlist?list=PLOZ3jentlCDAxKpBLMWogxSdy6BZcsAJq Trips & Tricks Channel ====================== https://www.youtube.com/channel/UCGmLfkuCo-3lHHJXRJ9HUMw Programming in Hindi Channel ============================ https://www.youtube.com/channel/UCudElIDgwNrybeAvXIy1HZQ
Views: 15176 ITORIAN
Oracle Unique Constraint تعليم اوراكل
 
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by Mohamed El Desouki - محمد الدسوقى [email protected] Tel :00966 553450836 جامعة سلمان بن عبد العزيز - السعودية - الخرج How To Add Unique Constraint to Table. Unique كيف تستخدم قيد الــ Text Book: Fundamentals of Database Systems, 5th Edition, by Elmasri/Navathe, published by Addison-W oracle create table statement oracle drop table statement oracle constraints database constraints primary key constraint foreign key constraint check constraint null not null constraint unique constraint
Oracle SQL Tutorial 12 - Intro to Constraints
 
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As I believe I've mentioned in an earlier video, a constraint is basically a rule we can put in our database that prevents someone from putting the wrong data in. It protects our relationships and data integrity. Because the goal of these constraints are to protect our data integrity, you may hear them called integrity constraints. There are many integrity constraints we are going to talk about: NOT NULL UNIQUE PRIMARY KEY FOREIGN KRY CHECK There is also the DEFAULT attribute. These are all keywords we can add to our columns that will change the way the database works with our data and also prevents incorrect data. NOT NULL is a constraint you can put on a column that prevents nulls. A null is the absence of a value. When we say null, we are saying that every single row has to have a value for this column. UNIQUE is a constraint that makes every row have a unique value for this column. Now note, this does not require values to be put it, and it will allow multiple rows to be null. Next, we are going to talk about primary keys. What qualifies a column as a candidate key? First, not a single row should have a null for that column. Second, every row must be unique. The primary key constraint is essentially a combination of the NOT NULL constraint and the UNIQUE constraint. The foreign key constraint sets the requirement that any value in this column for any row must match a row in another column. Check constraints allow us to be more strict with what data is allowed in our database. NOT NULL and UNIQUE give some level of restriction, but what if we want something more specific? For example, what if we only want values between 0 and 100? That is where check constraints come in. When using check constraints, you give a boolean expression. A boolean expression is something that can be evaluated to true or false. It will only insert the row if the value you try to put into the row makes the expression evaluate to true. So if you put in a value too great or small, the expression will be false and the data is not allowed to be entered. The default constraint is a value you can give a column, and if for any reason when the row is created in the table a value is not provided, the default value will be given. So for example, we could have a bank account table where the balance defaults to 0. How do you actually implement these constraints when you are creating a table? In the next video we are going to be adding these to our users table. Please be sure to subscribe! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon: http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 21357 Caleb Curry
Oracle SQL Tutorial 15 - How to Add Primary Key Constraints
 
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The goal of this video is to take the CREATE TABLE statement we have and walk through the different ways to create primary keys. This and foreign keys are the most common constraints, so we need to make sure that you have this one down. Once we have a more complex database design with multiple tables, we will learn the proper way to create foreign keys. For now, I am going to keep all of our constraints at the column level, unnamed. The only exception is the primary key, because that is what we are focusing on in this video. The first way to create the primary key is at the column level, unnamed. The primary key is very important because it what we use to distinguish rows from one another. Every table you create is going to need a primary key, and I suggest putting a lot of effort into making sure your keys are set up correctly and organized. --Delete the table if needed: DROP TABLE users; CREATE TABLE users( user_id NUMBER PRIMARY KEY, username VARCHAR2(50 CHAR) NOT NULL UNIQUE ) The next way is at the column level, but named: --Delete the table: DROP TABLE users; CREATE TABLE users( user_id NUMBER CONSTRAINT users_pk PRIMARY KEY, username VARCHAR2(50 CHAR)NOT NULL UNIQUE ) The general naming convention here is the table name followed by an underscore, followed by pk for primary key. Finally, the third way, which is at the table level, is the way we are going to create our primary key: --Delete the table: DROP TABLE users; CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) NOT NULL UNIQUE, CONSTRAINT users_pk PRIMARY KEY (user_id) ) Now, once you've created these constraints, you can use Oracle SQL Developer to find these constraints. Open your databases in the connections tab and find the table in the Tables folder. Double click your table and travel to the Constraints tab. You can tell here that the UNIQUE constraint still exists in this table, but it has a pretty disgusting name. It kind of wants to make me puke. Referencing that constraint in the future with that wacky name would be a burden. Engrave these three options in your head so that you can use any of them whenever you need and can read other peoples' code. Thank you for sticking with the series thus far. In the next video, we will be…doing something. See you then! :) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 15280 Caleb Curry
SQL tutorials 17: SQL Primary Key constraint,  Drop primary Key
 
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Blog link: http://www.rebellionrider.com/sql-primary-key.htm SQL tutorial on Primary key / SQL Primary key, In this tutorial you will learn about simple primary key, composute primary key, how to drop primary key. defining primary key using create table and alter table along with many other things. Tool used in this tutorial is SQL Developer. This tutorial series is part of SQL expert exam certification training. if you are preparing for SQL certification you can use my tutorials. This SQL Tutorial is a part of free training. Copy Cloud referral link || Use this link to join copy cloud and get 20GB of free storage https://copy.com?r=j7eYO7 Contacts E-Mail [email protected] Twitter https://twitter.com/rebellionrider Instagram http://instagram.com/rebellionrider Facebook. https://www.facebook.com/imthebhardwaj Linkedin. http://in.linkedin.com/in/mannbhardwaj/ Thanks for linking, commenting, sharing and watching more of our videos This is Manish from RebellionRider.com So Primary Key There are two types of Primary keys First is Simple primary Key: Primary key which Involves only one column and Second is Composite Primary Key: Primary Key which involves more than one column. We will start with Simple primary key. You can create Primary key either with Create Table statement of by using Alter table Statement. Let's define simple primary key using create table statements. With create table statement we can either define primary key at column level or at table level. We will start with defining Primary key at column level using create table statement. You just have to put keyword Primary key after data type and size of column while defining a column of a table. Here oracle server will create a primary key on product id with default constraint name which will be slightly difficult to understand. You can give your own name to your constraint which is also a good practice.
Views: 100885 Manish Sharma
Oracle SQL Tutorial 18 - How to Create Foreign Keys
 
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In this video we are going to be creating foreign keys. I highly recommend watching the previous video before you watch this one. Essentially, we are creating a very simple database for a system where we can create projects and add people to those projects. We started with the users table: --Delete the table if needed: --DROP TABLE users; CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, CONSTRAINT users_pk PRIMARY KEY (user_id) ); Now we are going to create a table for projects with a column that is a foreign key to the username. We're going to want to make this match data types: CREATE TABLE projects( project_id NUMBER, project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) ) Next, we need to add the column attributes we decided on last video: CREATE TABLE projects( project_id NUMBER, project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL ) NOT NULL because we want every project to have a creator, but we are not labeling UNIQUE because that means we could only have a specific username once in the table. We want to allow a user to create multiple projects. We also need to add a primary key: CREATE TABLE projects( project_id NUMBER, project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (username) ) Now, the question that remains is, how can I tell Oracle that I want the username to reference the username column of the other table? We have to make a foreign key constraint. As you've learned from the previous videos, there are about three ways to create constraints. You can do it inline at the column level, unnamed. You can do it at the column level, named, and you can do it at the Table level, named. Usually the table-level is preferred, but I will quickly remind you how to do all three again. CREATE TABLE projects( project_id NUMBER, project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL REFERENCES users (username), CONSTRAINT projects_pk PRIMARY KEY (project_id) ) This works, but if we want to name it, we should do this: CREATE TABLE projects( project_id NUMBER, project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL CONSTRAINT projects_users_fk REFERENCES users (username), CONSTRAINT projects_pk PRIMARY KEY (project_id) ) This works, but the preferred method is to do it at the table level: CREATE TABLE projects( project_id NUMBER, project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (project_id), CONSTRAINT projects_users_fk FOREIGN KEY (creator) REFERENCES users (username) ) Great! So you've learned how to create a foreign key, now we can see it inside of Oracle SQL Developer. One important thing when it comes to foreign keys is what happens when have data in your database and you try to delete the parent row that a row in the child table references? In the next video we are going to configure that using ON DELETE. See you all then and if you enjoy this series, please do me a huge favor by liking the video and subscribing to my YouTube channel. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 22699 Caleb Curry
How to create Unique Constraint on Column for already existing Table - Part 97
 
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SQL Server / T-SQL Tutorial Scenario: You are working as SQL Server developer, you need to create Unique Constraint on already existing table called dbo.Customer on column SSN. Link to scripts used in SQL Server / TSQL Tutorial Video http://www.techbrothersit.com/2016/05/how-to-create-unique-constraint-on_6.html Check out our website for Different SQL Server, MSBI tutorials and interview questions such as SQL Server Reporting Services(SSRS) Tutorial SQL Server Integration Services(SSIS) Tutorial SQL Server DBA Tutorial SQL Server / TSQL Tutorial ( Beginner to Advance) http://www.techbrothersit.com/
Views: 1043 TechBrothersIT
61. ALTER TABLE for Adding Constraint in Column SQL (Hindi)
 
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Please Subscribe Channel Like, Share and Comment Visit : www.geekyshows.com
Views: 9265 Geeky Shows
constraint in dbms/sql - (null / notnull, check, default , unique, primary key constraints)
 
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constraint in sql with examples, null / notnull, check, default , unique, primary key constraints dbms constraints, DBMS videos. .................................................... GATE lectures on SIGNAL AND SYSTEM - by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI1qBFREKxhFbBR8veKrYj60 GATE lectures on ANALOG ELECTRONICS - by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI0SzA4wJDv7EqfgCHaRtunH&disable_polymer=true DIGITAL COMMUNICATION by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI0-af8Lr1S5Bwbv4_-kbi-4 DIGITAL LOGIC DESIGN - by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI0V04wTbaqUWvcvAE_B98Qj DSP by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI1VEDhEOVNHrTs_pzt684ou signal and system by SHRENIK JAIN https://www.youtube.com/playlist?list=PLfP-D1tg0DI2Fpj_oV4VvLax4JJVL_kW2 DBMS by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI0D1MSTRXFr1X6bb_ZI0E7W ANALOG ELECTRONICS by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI3HaJdHpBu7XX-m9c6mANZk ANALOG ELECTRONICS-2 by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI3tNQmWNnSrGydZ1tQUSMXy OPERATING SYSTEM -by SHRENIK JAIN https://www.youtube.com/playlist?list=PLfP-D1tg0DI1U3Xe4ynk6ocVQl2qKoDoB CONTROL SYSTEM - by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI1Cwku-ZLD-ofrsLHd5dHQy Engineering Maths https://www.youtube.com/playlist?list=PLfP-D1tg0DI0Kavkv81ZvQI8g7VSiVIm_ VLSI - by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI2Sn1DVzGdIeGyuIUjhJ9zp Limits and Continuity - by Siddhant Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI3Ln9qhdNlIbRR1gAqrGXH0 INTEGRATED CIRCUIT (IC) by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI1yEx1fdhqA8jR5WtCJvQN5 IMAGE PROCESSING - by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI2F_PAG8Z6WxZgqBK0jG_-D PROBABILITY by Shrenik Jain https://www.youtube.com/playlist?list=PLfP-D1tg0DI2KD99RmEobWaLiG4bZPNPN .................................................... ANY DOUBT ? ASK ON FB page . facebook link : https://www.facebook.com/studysimplified/ quora link : https://www.quora.com/profile/Shrenik-Jain-51
Views: 16570 Shrenik Jain
Oracle - SQL - Check Constraint
 
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Oracle - SQL - Check Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Tutorial#58 How to Use Unique key Constraint in Oracle SQL Database| unique key Constraint in SQL
 
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How to use Unique Key Constraint in Oracle or what is Constraints and Types of Constraints in an Oracle SQL Database | integrity Constraints in SQL Unique Key Constraint is nothing but its allowing Unique and Null Values in Columns Explaining constraints and types of constraints in oracle or Constraints in Oracle SQL database or Constraints is nothing but a set of rules which is applied to the columns of any table in the database Assignment: Assignment link will be available soon: In this series we cover the following topics: SQL basics, create table oracle, SQL functions, SQL queries, SQL server, SQL developer installation, Oracle database installation, SQL Statement, OCA, Data Types, Types of data types, SQL Logical Operator, SQL Function,Join- Inner Join, Outer join, right outer join, left outer join, full outer join, self-join, cross join, View, SubQuery, Set Operator. follow me on: Facebook Page: https://www.facebook.com/LrnWthr-319371861902642/?ref=bookmarks Contacts Email: [email protected] Instagram: https://www.instagram.com/equalconnect/ Twitter: https://twitter.com/LrnWthR
Views: 27 EqualConnect Coach
45. Primary Key and Foreign Key Constraints in PL/SQL Oracle
 
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In this video you will learn about Primary Key and Foreign Key Constraints in PL/SQL Oracle. For Support =========== Email: [email protected] Contact Form: http://www.learninhindi.com/home/contact Our Social Media ================ Facebook: https://www.facebook.com/LearnInHindi Twitter: https://twitter.com/LearnInHindi For Training & Videos ===================== For more videos and articles visit: http://www.learninhindi.com Free Java Programming In Hindi Course ===================================== https://www.youtube.com/playlist?list=PLOZ3jentlCDAwwhMyoLISrxkXTADGp7PH Free Oracle PL/SQL Programming In Hindi Course ============================================== https://www.youtube.com/playlist?list=PLB5DA82419C2D99B6 Free C Programming In Hindi Course ================================== https://www.youtube.com/playlist?list=PLOZ3jentlCDAxKpBLMWogxSdy6BZcsAJq Trips & Tricks Channel ====================== https://www.youtube.com/channel/UCGmLfkuCo-3lHHJXRJ9HUMw Programming in Hindi Channel ============================ https://www.youtube.com/channel/UCudElIDgwNrybeAvXIy1HZQ
Views: 11046 ITORIAN
ORACLE BASIC 5|| UNIQUE KEY||CONSTRAINTS||STUDY EASY
 
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In this video we learn about how to add Unique key into table in oracle 10g
Views: 8 Study Easy
Oracle - SQL - Constraints
 
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Oracle - SQL - Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Tutorial 14 - Column-Level and Table-Level Constraints
 
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In the previous video we talked about adding constraints at the column-level. We made it nice and simple by only requiring a few keywords, but the problem we were having is that we could not assign a name to the constraint, which many people like to do so we can reference easily if we need to at a later time. To do this, it requires a little bit more typing, but it will give us extra flexibility and many consider it to be the higher quality approach to adding constraints. Let's go though a simple example. Let's say we have a users table with a user_id column that we want to make a primary key. We will create the table like this: CREATE TABLE( user_ id NUMBER PRIMARY KEY ) Instead of adding the PRIMARY KEY keywords after the data type, we add: CONSTRAINT user_pk PRIMARY KEY Now, we have assigned the name user_pk to this constraint. You can do the same with other constraints, such as UNIQUE. The syntax would be CONSTRAINT username_un UNIQUE. The other way to create constraints requires to put all of our constraints at the bottom of our table creation rather than inline with the column. This type of constraint is known as a table-level constraints. To make a column a primary key using table-level constraints, we add it to the CREATE TABLE command as if it is another row and use the CONSTRAINT keyword to tell Oracle that what is coming is a constraint, not a column in our table. CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR), CONSTRAINT username_un UNIQUE (username), CONSTRAINT users_pk PRIMARY KEY (user_id) ) The primary differences here is that you have to put the column you are talking about in parenthesis after the PRIMARY KEY keyword. That's because it's at the end of the table and you need a way to tell it what column you are talking about. The option of putting it at the end of the table has the added benefit in this situation because if we needed to have a primary key that is the combination of multiple columns, we can do that by just adding the other column in the PRIMARY KEY parenthesis right after a comma. In summary, there are three ways to make constraints. The first is at the column level, unnamed. The second is at the column level, named. The third is at the table level, also named. In the next video we are going to create a named constraint in Oracle SQL Developer, so stay tuned and be sure to subscribe! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 15583 Caleb Curry
Oracle Sql 4: alter table constraints
 
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add y drop check, unique, primary key
Views: 1532 tomas bonilla
Oracle - SQL - Alter Table
 
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Oracle - SQL - Alter Table Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
drop primary key,not null,unique,default and check constraints from columns in a table
 
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This video explains how to drop primary key,not null,unique,default and check constraints with or without constraint name in a table link to HOW to add constraint while creating table: https:// https://www.youtube.com/watch?v=dh_UKs-LnK8 link to how to add new columns with constraints : https://www.youtube.com/watch?v=UNAatxnnwB8 link to how to add constraints to existing column https://www.youtube.com/watch?v=02_fXRQpwSc how to drop all constraints on the table: https://www.youtube.com/watch?v=CM7FPqIr6gc subscribe - https://www.youtube.com/channel/UCNl7...
Views: 2105 kwl zerotwonine
Oracle - SQL - Not Null Constraint
 
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Oracle - SQL - Not Null Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle||Oracle Integrity Constrants Patr -1 by Dinesh
 
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Table Constraints in SQL: NOT NULL, DEFAULT, UNIQUE, and CHECK
 
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This SQL tutorial discusses the common constraints one can place on a table: NOT NULL, DEFAULT, UNIQUE, and CHECK, including the purpose of each constraint, as well as how to apply each constraint to a table during table creation. 0:24 NOT NULL Constraint 0:56 DEFAULT Constraint 2:03 UNIQUE Constraint 2:34 CHECK Constraint
Views: 8727 1Keydata
Primary Key, Foreign Key, NOT NULL, DEFAULT, UNIQUE, and CHECK   ||  Table Constraints in SQL
 
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primary key Learn SQL - SQL CONSTRAINTS CONSTRAINTS - PRIMARY KEY, NOT NULL, etc - SQL Server constraints in dbms | constraints in sql in hindi Oracle SQL Tutorial - How to Add Column Constraints (Attributes) Oracle SQL Constraints Not Null, Primary Key, Unique, Foreign Key and Check Primary Key (PK) Constraint in SQL Server Unique key constraint SQL constraints Working with Primary & Foreign key Constraint in SQL Server | MSSQL Training NOT NULL, DEFAULT, CHECK Constraints (Domain Integrity) in SQL Server Introduction to SQL Constraints
Oracle 12C Tutorial 20 - Constraints (Primary, Foreign, Unique, Null etc.)
 
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This Video Tutorial Will Describe about various constraints we can use with tables. Some of the constraints can used as table level or column level so also known as table level constraints and column level constraints. These command will also work on other versions of database like Oracle 11g Database, Oracle 10g Database, Oracle 9i Database, Oracle 8i Database, Oracle 8 Database and so on. In this video i explain Not Null Constraint, Unique key Constraint, Primary Key Constraint, Foreign Key - Reference key Constraint, Check constraint and user_constraints table. Full Syntax will be given in this video tutorial about how to use these constraints. Along with live example to execute Not Null Constraint, Unique key Constraint, Primary Key Constraint, Foreign Key - Reference key Constraint, Check constraint and user_constraints table . All the keywords, format, mandatory clauses etc are described in this video.
Oracle SQL Tutorial 21 - How to Create / Drop Indexes
 
03:58
In the last video, we wrote up the SQL to create three tables: CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, CONSTRAINT users_pk PRIMARY KEY (user_id) ); CREATE TABLE projects( project_id NUMBER, Project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (project_id), CONSTRAINT projects_users_fk FOREIGN KEY (creator) REFERENCES users (username) ON DELETE CASCADE ); CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ); I'm going to increase the size of the users table a bit by adding a first and last name column. CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, first_name VARCHAR2(50 CHAR), last_name VARCHAR2 (50 CHAR), CONSTRAINT users_pk PRIMARY KEY (user_id) ); But before we finish this design, we should consider indexing certain columns. What columns should we index? Well, as a reminder, the columns that are indexed by default are columns with the UNIQUE constraint, and those that are labeled as primary keys. Columns that are not indexed but often should be are those labeled as a foreign key. The column that jumps out the most to me is the creator column of the project table. It's the only foreign key that is not part of some index. Let's fix this by creating our first index. The way we do that is with the CREATE INDEX command. CREATE INDEX projects_creator_ix ON projects (creator) What naming convention are we following for the index? We are naming it by the table name, followed by an underscore, followed by the column, followed by an underscore, followed by an ix (for index). In this situation it does not apply, but if our foreign key column is labeled as UNIQUE, we can add the UNIQUE keyword like this: CREATE UNIQUE INDEX projects_creator_ix ON projects (creator) Now if you want to get rid of an INDEX, you can use this command: DROP INDEX projects_creator_ix Now, if we want to select data from the user table and the project table we can do that much faster. That's because the foreign key and column it references are both indexed and those are the columns we would do the join on. We will discuss how to do joins in a future video. So what are some potential problems with this database design? Overall, it is pretty good. With this design though we need to make sure there is no way for someone to update a user's username. In the next video we are going to discuss why. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 8935 Caleb Curry
Oracle Drop, Disable and Enable Constraints تعليم اوراكل
 
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by Mohamed El Desouki - محمد الدسوقى [email protected] Tel :00966 553450836 جامعة سلمان بن عبد العزيز - السعودية - الخرج How to Drop , Disable and Enable Constraints. كيف حذف و تعطيل و إعادة تشغيل القيود Text Book: Fundamentals of Database Systems, 5th Edition, by Elmasri/Navathe, published by Addison-W oracle create table statement oracle drop table statement oracle constraints database constraints primary key constraint foreign key constraint check constraint null not null constraint unique constraint
Unique Constraint in Oracle in Telugu
 
13:59
#KOTHA_ABHISHEK http://htmlintelugu1.blogspot.com http://cssintelugu1.blogspot.com http://javascriptintelugu1.blogspot.com http://sqlintelugu1.blogspot.com http://javaintelugu1.blogspot.com
Views: 557 KOTHA ABHISHEK
Oracle - SQL - Primary Key Constraint
 
04:10
Oracle - SQL - Primary Key Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
How to Resolve Oracle SQL Parent Key Not Found (ORA-02291)
 
05:49
In this video, we’ll explain what the ORA-02291 “parent key not found” error is, see an example, and look at how to resolve it. This error usually happens when we try to insert data into a table. It looks like this: Error is: ORA-02291: integrity constraint (constraint_name) violated - parent key not found So what does this error mean? It means we’re trying to insert data into a child table, and there is no related record in the parent table. If a foreign key has been set up to enforce this relationship, there needs to be a parent to insert a child that refers to it. Watch the video to see an example of this error as well as how to resolve it. For more information on Oracle SQL, refer to the Database Star website here: https://www.databasestar.com/
Views: 2957 Database Star
DIFFERENCE BETWEEN PRIMARY KEY AND UNIQUE KEY CONSTRAINT IN ORACLE SQL
 
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This video tutorial explains about the difference between primary key and unique key in oracle sql which is also a to be asked interview quiestion. After watching this video you will be able to explain the difference between both the constraints.
Views: 2189 Kishan Mashru
47. UNIQUE KEY in SQL (Hindi)
 
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Please Subscribe Channel Like, Share and Comment Visit : www.geekyshows.com
Views: 20214 Geeky Shows
Oracle Foreign key Constraint تعليم اوراكل
 
13:24
by Mohamed El Desouki - محمد الدسوقى [email protected] Tel :00966 553450836 جامعة سلمان بن عبد العزيز - السعودية - الخرج How To Combine two tables using Foreign Key Constraint.ربط الجداول بإستخدام قيد Text Book: Fundamentals of Database Systems, 5th Edition, by Elmasri/Navathe, published by Addison-W oracle create table statement oracle drop table statement oracle constraints database constraints primary key constraint foreign key constraint check constraint null not null constraint unique constraint
SQL Server 26 - PRIMARY KEY, NOT NULL, UNIQUE
 
03:36
In the last video we created our first table, but I want to give SQL Server some extra information so the database knows more about each of the columns. The first thing is to establish the primary key. To do this all we do is add PRIMARY KEY after the column we want to be the primary key. Simple enough. When we add a constraint right after the column like this, it is often called a column attribute. CREATE TABLE Animals( ID INT PRIMARY KEY, Name VARCHAR(50), Species VARCHAR(50) ); Additionally, if you are using an ID column, it is best to have it labeled as the IDENTITY column. That way, SQL Server will automatically increment the number. CREATE TABLE Animals( ID INT PRIMARY KEY IDENTITY, Name VARCHAR(50), Species VARCHAR(50) ); The other attributes we've discussed in this series are NOT NULL and UNIQUE. We can make the name NOT NULL and the species NOT NULL. We don't have a good column for UNIQUE, so let's add one: CREATE TABLE Animals( ID INT PRIMARY KEY IDENTITY, Name VARCHAR(50) NOT NULL, Species VARCHAR(50) NOT NULL, ContactEmail VARCHAR(50) NOT NULL UNIUQE ); You can see that it is very easy to add multiple column attributes to a column. Just separate them by spaces. The order does not matter. Also, when you say primary key the column is automatically NOT NULL and UNIQUE. There are other attributes you can use including DEFAULT, FOREIGN KEY, and SPARSE. DEFAULT will give a value for a column if you do not put anything in yourself. Foreign keys are used to reference other columns. SPARSE is an attribute we haven't discussed. You can use SPARSE if most of the rows are going to have a NULL for a column and it saves storage space, but we will worry about that in another video. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 4853 Caleb Curry
Oracle SQL Tutorial 20 - How to Create Composite Primary Keys
 
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This video is going to be a tutorial on how to create composite and compound keys. The difference between a composite and compound key is that a composite key can consist of any columns while a compound key has to consist of columns that are all keys themselves. We will be working with a compound key because we are going to be using the an intermediary table that has two foreign keys. The combination of both of the keys have to be unique. First, if we have any other CREATE TABLE commands, we are going to comment those out. We will space out the CREATE TABLE to have each column on a line, then we will add constraints as needed. CREATE TABLE project_users( project_id, user_id ) Now, let's add the data types: CREATE TABLE project_users( project_id NUMBER, user_id NUMBER } Now, what about some column attributes? I'm going to make both of the columns NOT NULL because we always want the rows to have a user and a project: CREATE TABLE project_users( project_id NUMBER NOT NULL, user_id NUMBER NOT NULL } Now, let's add the foreign key constraints. Now, what do we name these? We are going to add a primary key that covers both of these columns, so I'm going to be a sinner and not give these constraints names: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id), user_id NUMBER NOT NULL REFFERENCES users (user_id) ) Now, the way we have it now is that if we delete a project in the project table, and there are any rows in the project_users table, it will throw an error and prevent deletion. I would prefer for it to also delete any project members. That would make sense because if you delete a project we want it to delete the associate between that project and certain users. The same goes for if we delete a user, we want their association with a certain project to be deleted. To do this, we need to add the ON DELETE command: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, ) Finally, let's learn how to create a compound or composite key. literally, the only difference is that you put a comma and add the second table inside of the parenthesis. CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ) Now, the combination of project_id and user_id cannot be null, is always unique, and has an index. The only thing we should do now is add a few indexes. We aren't done yet...In the next video we are going to figure out what columns would benefit from indexes and we'll add them to it. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 11237 Caleb Curry
P#5 difference between primary and unique key constraints in oracle SQL - interview question
 
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Tutorial on what is the difference between Primary key and Unique key this frequently asked question will help you in Oracle SQL database interview question This will clear few concepts of Constraint and over here the difference between Primary and unique key in oracle explained with the example or where to use Primary Key and where to use Unique Key in Oracle sql This will cover the Following question: 1) Primary key V/s unique key 2) primary and unique 3) primary and unique key in sql 4) difference between primary and unique key with example 5) difference between the primary and unique key in oracle 6) constraints in oracle 7) constraints in oracle with example 8) how to check constraints on a table in oracle ( will cover latter) 9) constraints in SQL how to find constraints on a table in desc table name drop constraint sql server alter table tablename drop constraint constraintName; follow me on: Facebook Page: https://www.facebook.com/LrnWthr-319371861902642/?ref=bookmarks Contacts Email: [email protected] Instagram: https://www.instagram.com/equalconnect/ Twitter: https://twitter.com/LrnWthR #equalConnectCoach #rakeshmalviya #Oracleconstraints
Views: 34 EqualConnect Coach
Oracle - SQL - Foreign Key Constraint
 
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Oracle - SQL - Foreign Key Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Programming - Constraints
 
31:37
This video demonstrates the use and syntax for 5 constraint types in Oracle: Primary Key, Foreign Key, Unique, Check, and Not Null.
Views: 213 Brian Green
PRIMARY KEY and UNIQUE KEY Constraints in Oracle Database
 
09:22
unique constraint oracle oracle check constraint alter table add constraint primary key oracle oracle unique constraint multiple columns oracle unique constraint vs unique index
Views: 8 Adam Tech
Primary key and Foreign key on Oracle In Telugu | Oracle in Telugu
 
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#KOTHA_ABHISHEK http://htmlintelugu1.blogspot.com http://cssintelugu1.blogspot.com http://javascriptintelugu1.blogspot.com http://sqlintelugu1.blogspot.com http://javaintelugu1.blogspot.com
Views: 5620 KOTHA ABHISHEK
Oracle Tutorials | Unique, Not Null & Check  Constraints in Oracle Part- 1 | by Mr.Sudhakar L
 
14:24
Oracle Tutorials | Unique, Not Null & Check Constraints in Oracle | by Mr.Sudhakar L #Oracle #Constraints #Tutorials ** For Online Training Registration: https://goo.gl/r6kJbB ► Call: +91-8179191999 ► Visit Our Website for Classroom Training: https://nareshit.in ► For Online Training: https://nareshit.com/ -------------------------- ► About NareshIT: "Naresh IT is having 14+ years of experience in software training industry and the best Software Training Institute for online training, classroom training, weekend training, corporate training of Hadoop, Salesforce, AWS, DevOps, Spark, Data Science, Python, Tableau, RPA ,Java, C#.NET, ASP.NET, Oracle, Testing Tools, Silver light, Linq, SQL Server, Selenium, Android, iPhone, C Language, C++, PHP and Digital Marketing in USA,Hyderabad, Chennai and Vijayawada,Bangalore India which provides online training across all the locations -------------------------- ► Our Online Training Features: 1.Training with Real-Time Experts 2.Industry Specific Scenario’s 3.Flexible Timings 4.Soft Copy of Material 5. Share Videos of each and every session. -------------------------- Please write back to us at [email protected]/[email protected] or Call us at USA: +1404-232-9879 or India: +918179191999 ** Check The Below Links** ► For Course Reg: https://goo.gl/r6kJbB ► Subscribe to Our Channel: https://goo.gl/q9ozyG ► Circle us on G+: https://plus.google.com/NareshIT ► Like us on Facebook: https://www.facebook.com/NareshIT ► Follow us on Twitter: https://twitter.com/nareshitech ► Follow us on Linkedin: https://in.linkedin.com/company/naresh-i-technologies ► Follow us on Instagram: https://www.instagram.com/nareshitech/
Oracle 12C Tutorial 20 - Constraints Primary, Foreign, Unique, Null etc
 
19:41
This Video Tutorial Will Describe about various constraints we can use with tables. Some of the constraints can used as table level or column level so also known as table level constraints and column level constraints. These command will also work on other versions of database like Oracle 11g Database, Oracle 10g Database, Oracle 9i Database, Oracle 8i Database, Oracle 8 Database and so on. In this video i explain Not Null Constraint, Unique key Constraint, Primary Key Constraint, Foreign Key - Reference key Constraint, Check constraint and user_constraints table. Full Syntax will be given in this video tutorial about how to use these constraints. Along with live example to execute Not Null Constraint, Unique key Constraint, Primary Key Constraint, Foreign Key - Reference key Constraint, Check constraint and user_constraints table . All the keywords, format, mandatory clauses etc are described in this video. The background music comes from Ross Bugden - Music channel. Link mentioned below: https://www.youtube.com/channel/UCQKGLOK2FqmVgVwYferltKQ and music link is : https://www.youtube.com/watch?v=BY0U432m8W0
Views: 18 game hounds
What is the Difference between Primary Key and Unique Key - Database Tutorial 14
 
04:51
Database Tutorial. This video is about Database Fundamentals. I hope this series of videos can help those who want to be Database Professionals. I will cover various database technologies including Oracle Database, Microsoft SQL Server database and Sybase. Video: What is the Difference between Primary Key and Unique Key (Video 14 in the Database Tutorial Series) (Common for Oracle/Microsft SQL Server/Sybase /MySQL)
Views: 34942 Sam Dhanasekaran
Working with Primary & Foreign key Constraint in SQL Server | SQL Server Tutorial
 
24:13
** For Online Training Registration: https://goo.gl/r6kJbB ? Call: +91-8179191999 💡 Visit Our Website for Classroom Training: https://nareshit.in/sql-server-training/ 💡For Online Training: https://nareshit.com/course/sql-server-online-training/ #sqlserver #server #programming #course #Tutorials #Training #Videos -------------------------- -------------------------- 💡 About NareshIT: "Naresh IT is having 14+ years of experience in software training industry and the best Software Training Institute for online training, classroom training, weekend training, corporate training of Hadoop, Salesforce, AWS, DevOps, Spark, Data Science, Python, Tableau, RPA , Java, C#.NET, ASP.NET, Oracle, Testing Tools, Silver light, Linq, SQL Server, Selenium, Android, iPhone, C Language, C++, PHP and Digital Marketing in USA, Hyderabad, Chennai and Vijayawada, Bangalore India which provides online training across all the locations -------------------------- 💡 Our Online Training Features: 🎈 Training with Real-Time Experts 🎈 Industry Specific Scenario’s 🎈 Flexible Timings 🎈 Soft Copy of Material 🎈 Share Videos of each and every session. -------------------------- 💡 Please write back to us at 📧 [email protected]/ 📧 [email protected] or Call us at the USA: ☎+1404-232-9879 or India: ☎ +918179191999 -------------------------- 💡 Check The Below Links ► For Course Reg: https://goo.gl/r6kJbB ► Subscribe to Our Channel: https://goo.gl/q9ozyG ► Circle us on G+: https://plus.google.com/+NareshIT ► Like us on Facebook: https://www.facebook.com/NareshIT ► Follow us on Twitter: https://twitter.com/nareshitek ► Follow us on Linkedin: https://goo.gl/CRBZ5F ► Follow us on Instagram: https://goo.gl/3UXYK3
Views: 63228 Naresh i Technologies
Constraint In Oracle PL SQL
 
06:47
Constraint In Oracle PL SQL oracle tutorial for beginners A) UNIQUE CONSTRAINT : A unique constraint is uniquely defines a record. Its value is not repeated. It can be null. B)NOT NULL CONSTRAINT: Not null constraint restrict from inserting null values. If we want some columns does not take null values then we can use this constraint. C)CHECK CONSTRAINT: A check constraint allows you to specify a condition on particular column in a table. we can add our custom logical conditions. CREATE TABLE TEST2 ( ID VARCHAR2(10) UNIQUE, NAME VARCHAR2(50), DEPT VARCHAR2(10) NOT NULL, AGE NUMBER(10), CHECK (AGE BETWEEN 18 and 60) ); #techquerypond https://techquerypond.wordpress.com https://techquerypond.com https://twitter.com/techquerypond
Views: 189 Tech Query Pond
Oracle - SQL - Managing Constraints
 
06:01
Oracle - SQL - Managing Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle Tutorial || Oracle| Sql Constraints Part - 1 by basha
 
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DURGASOFT is INDIA's No.1 Software Training Center offers online training on various technologies like JAVA, .NET , ANDROID,HADOOP,TESTING TOOLS ,ADF,INFORMATICA,TABLEAU,IPHONE,OBIEE,ANJULAR JS, SAP... courses from Hyderabad & Bangalore -India with Real Time Experts. Mail us your requirements to [email protected] so that our Supporting Team will arrange Demo Sessions. Ph:Call +91-8885252627,+91-7207212428,+91-7207212427,+91-8096969696. http://durgasoft.com http://durgasoftonlinetraining.com https://www.facebook.com/durgasoftware http://durgajobs.com https://www.facebook.com/durgajobsinfo......
Oracle SQL Tutorial 16 - Parent Child Relationships
 
06:09
So far in this series we have discussed database design, creating tables, and constraints. We've brought up the concept of foreign keys, but we have not explained how to create them. That is the goal of this video and the upcoming videos. We want to study those foreign keys! Let's make them not so foreign. Let's learn the proper way to define a foreign key. As a reminder, a foreign key is a column that references a column of another table. The column it references must either be a primary key, or have the UNIQUE constraint. This means that every value inside of the column that is labeled as a foreign key, there must be that value in some row of the referenced column. As an example, imagine that we have the users table, and we have a table service_requests. We could have a column in the service_request that references a column in the users table. Usually this would be the primary key that is referenced, but there is nothing stopping you from referencing a unique column. Just for fun, let's go through an example using the username column. If we have a service_requests table, every single row within the table is going to be what some would consider an instance of a service_request. This means that the table columns are like the blueprint for what a service request looks like and then each row is an individual service request. If we have one of the columns labeled as a foreign key to the username of the users table, what does that mean practically? It means that for a single row, the value for that column must be a value that exists in the users table. We could have a service_request submitted by a user with the username of Yoloswagman. This means that there must be a row inside of the users table that has the value Yoloswagman for the username column. This brings up the concept of parent and child relationships. Yoloswagman in this situation is the parent, and his service request is the child. When we draw it out, it makes sense why a primary key must be UNIQUE. If we had two Yoloswagmans, the child would not know which column is the parent. The same applies if we were using IDs and we had So remember, always reference a primary key or a column with the UNIQUE constraint. Now, I have a question for you. Do foreign keys automatically have the UNIQUE constraint, just like primary keys? The answer is no. A parent row can have many child rows. It makes sense because the user could submit multiple service requests. Can we force the column to be unique? Absolutely. If that was the case, the user could only make one service request. Another question. Do foreign keys automatically have the NOT NULL constraint, just like primary keys? The answer is no. Essentially what this means is that a child could be created with no parent. Can we force the column to be NOT NULL? Absolutely. It is ok in some situations to allow the row to be null, but in this situation it makes no sense. It would be wise for us to add that constraint ourselves. So now that you understand some more differences between primary and foreign keys and parent child relationships, take all of these questions into consideration when you are creating foreign keys. In the next video, we are going to start a small project that is going to require multiple tables. We'll take a video to design our structure and then we'll get to creating those foreign keys in Oracle SQL Developer. Stick around and if you like these videos please be a serious supporter and subscribe to my channel. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 12935 Caleb Curry
SQL Server 27 - How to Create FOREIGN KEY Constraints
 
04:25
In the previous video we set up an entire table. The problem with this table is that the species column is just plain text. The problem with this is that there is a higher probability of incorrect data and if we have tons of animals in here there will be a lot of redundant information. The solution to this is to change this species to a foreign key to another table. Remember that when you create a foreign key it is a child to a parent. The thing you need to know is that the parent has to exist before the child so the child has something to reference. So let's create the parent table. CREATE TABLE Species( ID INT PRIMARY KEY IDENTITY, Species VARCHAR(50) NOT NULL UNIQUE, FriendlyName VARCHAR(50) NOT NULL //NOT UNIQUE because multiple rows could be same category (Ex: Bunny) ); Now, the friendly name will likely have redundant data, so maybe later we can add a table for animal categories or something, but let's not overwhelm ourselves quite yet. Maybe in a few videos. Now that we have created that table, we can recreate the table that references it. The first thing to know when creating a foreign key is that the data type must match. Because the ID column in the species table is of type INT, we should make our Species column in the Animals table also of type INT. Secondly, to make this a foreign key we add REFERENCES Species(ID) to the Species column. DROP TABLE IF EXISTS Animals; CREATE TABLE Animals( ID INT PRIMARY KEY IDENTITY, Name VARCHAR(50) NOT NULL, Species INT NOT NULL REFERENCES Species(ID), ContactEmail VARCHAR(50) NOT NULL UNIQUE ); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 6331 Caleb Curry