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Oracle SQL Tutorial 19 - ON DELETE (SET NULL and CASCADE)
 
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Welcome everyone! Something you need to consider when you are creating foreign keys is what happens if you delete the parent? As a reminder, the parent is the row that has the value you are referencing in the row that has a foreign key. Why is this something important to consider? It's important because foreign keys need to protect us from two primary things, unacceptable INSERT statements, and unacceptable DELETE statements. Let's see what happens when we try to insert incorrect data into the table with the foreign key: INSERT INTO projects VALUES (1, 'Update website homepage', 'CalebCurry') The response tells us plainly that there is no such user in the users table. So this works correctly. Deleting data on the other hand works a bit differently because the database does not know what you want to do with the child row when you delete the parent from the parent table. By default, we will get an error message that prevents the parent from being deleted, but there are some other options. How do we configure this? This is where the ON DELETE statement comes in. We add the keywords ON DELETE right after the foreign key and then we can give it the option of CASCADE or SET NULL. CASCADE means that if we delete the parent, we are also going to delete the child. In our situation what that means is that if somebody creates a project in our project table and then that persons account gets deleted, all of the projects he owns will also be deleted. CASCADE: 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 ) SET NULL will take the value in the child table and get rid of it. What you are left with is NULL. This means that we have an orphaned child. The first thought you might have is that it is a bad thing to have an orphaned child, but in databases that is not always so. In our application if we had it set to SET NULL, when a user account gets deleted the projects would remain in existence they would just lack a creator. This might be a good thing if you are concerned about the long term survival of a project, this might be the route you want to go. It ultimately depends on the application purpose. If you don't like CASCADE or SET NULL, you can leave the entire ON DELETE statement and just have Oracle throw an error when a parent is deleted. As for us, we are going to use ON DELETE CASCADE. We need to use this with extreme caution. If you are not careful, someday you will run a delete a row and that will cascade through you database deleting a bunch of stuff you didn't want to delete. Stuff happens, so make sure you back up your database every once in eternity. Now, in the last video we started with a database design that had three tables. We've only created two in this video. In the next video we are going to create the next one, which is a little special. Then we'll finish things up by adding some indexes. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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: 19087 Caleb Curry
118. ON UPDATE SET NULL in SQL (Hindi)
 
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Views: 3536 Geeky Shows
SQL Tutorial - 21: The UPDATE Query
 
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In this tutorial we'll check out the UPDATE Query which is used to update/change records in a table.
Views: 97837 The Bad Tutorials
NULL Value in Oracle Database | Oracle Tutorials for Beginners
 
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NULL Value in Oracle Database | Oracle Tutorials for Beginners NULL Value in Oracle Database NULL Value in Oracle SQL NULL Value in SQL NULL Value in Oracle Database Oracle Tutorials for Beginners Oracle Tutorials for Beginners Oracle PL/SQL Tutorials for Beginners Oracle PL/SQL Tutorials for Beginners Oracle PL/SQL Tutorials for Beginners how to select null values in oracle oracle compare null values in where clause null=null in oracle how to handle null in case statement in oracle how to check null value in oracle stored procedure oracle nvl null value in oracle query how to check empty column value in oracle how to select null values in oracle oracle is null vs = null oracle nvl oracle is not null oracle decode oracle isnull oracle case when null select null from table in oracle oracle compare null values in where clause oracle select null how to check empty column value in oracle oracle sql not null or empty oracle is not null how to handle null in case statement in oracle oracle isnull oracle nvl
Views: 855 Oracle PL/SQL World
SQL tutorial 19: ON DELETE SET NULL clause of Foreign Key By Manish Sharma (RebellionRider)
 
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SQL Tutorial 19 : ON DELETE SET NULL foreign key Clause. Links used in the tutorial On delete set null website article [ download SQL script from same link] : http://www.rebellionrider.com/on-delete-set-null.htm Foreign Key Tutorial Video : http://youtu.be/0nbkBI5r3Gw Foreign Key Tutorial Blog : http://www.rebellionrider.com/sql-foreign-key.htm This video is the part of foreign key video In this sql tutorial you will learn the referential clause ON DELETE SET NULL of foreign key. On Delete Set null clause guarantee the relation integrity in foreign key/ 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 liking, commenting, sharing and watching more of our videos This is Manish from RebellionRider.com
Views: 50089 Manish Sharma
SQL Server 17 - ON DELETE and ON UPDATE
 
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Now, what happens when you have successfully created a reference, and now you try deleting the parent? This is where the ON DELETE clause comes in. This is essentially how we configure how strict a foreign key is. There are 4 options you can give for an ON DELETE: Standard SQL Server NO ACTION Yes (Default) CASCADE Yes SET NULL Yes SET DEFAULT Yes Now the default is NO ACTION. This means that when you try to delete a parent row, SQL Server is going to throw an error and not let you. Cascade means that if you delete the parent row, any rows that reference that parent will also be deleted. This is pretty dangerous and not often recommended. SET NULL will set the foreign key to be NULL. Now obviously, this is going to require that the foreign key is not labelled NOT NULL. Finally, set DEFAULT will change the reference to the child row to some default value. We have not discussed defaults, but a column can have a default value. For example, we could make a deleted user in our Users table, and set the default for the foreign key to be the deleted user, and when any other users are deleted it will default to the deleted user UserId. In addition to the ON DELETE clause, there is the ON UPDATE clause. This one is a little less common because it configures what happens when a parent value changes. Obviously, when you are referencing a primary key, the ON UPDATE clause is nearly useless. That's because the primary key value is never supposed to change. If, on the other hand, we have a foreign key referencing a UNIQUE column that is not a primary key, it may change occasionally. So the only times you have to worry about the ON UPDATE clause is with foreign keys referencing UNIQUE columns that are not a primary key, and when you have natural keys that break the rules and actually do change at some point in time. The ON UPDATE clause has the same options as the ON DELETE clause and they all work the same way. Now, the last thing you need to know about foreign keys is that they must match the data type of the column you are referencing. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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: 6586 Caleb Curry
ON DELETE CLAUSE OF FOREIGN KEY CONSTRAINT IN ORACLE SQL WITH EXAMPLE (CASCADE/SET NULL/NO ACTION)
 
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This is a free video tutorial explaining about the nonmandatory on delete clause in the foreign key constraint in Oracle SQL database, the video explains about how the on delete set null and on delete cascade works, how it can be implemented with easy to understand examples. We have also shown practical demonstration on creating the foreign key constraint, and then deleting the data from the parent table and observing the changes that take place in the child table.
Views: 1589 Kishan Mashru
114. ON DELETE SET NULL in SQL (Hindi)
 
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Please Subscribe Channel Like, Share and Comment Visit : www.geekyshows.com
Views: 5139 Geeky Shows
T SQL Lesson13 ON DELETE,ON UPDATE CASCADE/ NO ACTION/ SET NULL/ SET DEFAULT Bhaskar Reddy
 
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Jamie King of Neumont University showing the differences between CASCADE, SET DEFAULT, NO ACTION with foreign keys. Komplette Liste der Videos und zusätzliches Material auf Informatik, Uni Saarland: Bachelor: . Now, what happens when you have successfully created a reference, and now you try deleting the parent? This is where the ON DELETE clause comes in.
Views: 53 Trenton Kim
13.52 ON DELETE NO ACTION, SET NULL, CASCADE, SET DEFAULT
 
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Komplette Liste der Videos und zusätzliches Material auf http://datenbankenlernen.de Informatik, Uni Saarland: Bachelor: http://www.cs.uni-saarland.de/index.php?id=52&L=1&source=1352 Master: http://www.cs.uni-saarland.de/index.php?id=132&L=1&source=1352 Ph.D./Grad School: http://gradschool.cs.uni-saarland.de/&source=1352
MySQL 17 - ON DELETE and ON UPDATE
 
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Now, what happens when you have successfully created a reference, and now you try deleting the parent? This is where the ON DELETE clause come in. This is essentially how we configure how strict a foreign key is. There are 3 options you can give for an ON DELETE: RESTRICT / NO ACTION Yes - In MySQL they are the same, but not all DBMS. CASCADE Yes SET NULL Yes Now the default is RESTRICT. This means that when you try to delete a parent row, MySQL is going to throw an error and not let you. Cascade means that if you delete the parent row, any rows that reference that parent will also be deleted. This is pretty dangerous and not often recommended. SET NULL will set the foreign key to be NULL. Now obviously, this is going to require that the foreign key is not labelled NOT NULL. In addition to the ON DELETE clause, there is the ON UPDATE clause. This one is a little less common because it configures what happens when a parent value changes. Obviously, when you are referencing a primary key, the ON UPDATE clause is nearly useless. That's because the primary key value is never supposed to change. If, on the other hand, we have a foreign key referencing a UNIQUE column that is not a primary key, it may change occasionally. So the only times you have to worry about the ON UPDATE clause is with foreign keys referencing UNIQUE columns that are not a primary key, and when you have natural keys that break the rules and actually do change at some point in time. The ON UPDATE clause has the same options as the ON DELETE clause and they all work the same way. Now, the last thing you need to know about foreign keys is that they must match the data type of the column you are referencing. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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: 17233 Caleb Curry
SQL Error: Cannot insert the value NULL into column ID
 
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https://codedocu.com/Details?d=2139&a=10&f=352&l=0 System.Data.SqlClient.SqlException occurred HResult=0x80131904 Message=Cannot insert the value NULL into column 'IDDetail', table column does not allow nulls. INSERT fails.
Views: 8183 CodeDocu_com
Merge Statement in Oracle SQL with Example (UPDATE/DELETE or INSERT)
 
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This video demonstrates how to write a Merge Statement in oracle sql, how it is useful in doing a conditional update or delete or both of them when the condition between the target table and source table is evaluated to true, and how we can insert the record into the target table when condition is evaluated to false. The video also shows the use of UPDATE, DELETE and INSERT with Merge, and also the various possible ways to use a Merge statement!!!
Views: 10407 Kishan Mashru
Oracle Using In , Between and Not تعليم أوراكل
 
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by Mohamed El Desouki - محمد الدسوقى [email protected] Tel :00966 553450836 جامعة سلمان بن عبد العزيز - السعودية - الخرج How to use In , Between and Not. 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 insert into statement update statement delete statement select statement basic query where clause select where Like '%' Like '_' select where Like select where Between Between , Not Between select where In , Not In
SQL Null or Empty   How to Check for Null or Empty Column in SQL Server   SQL Training Online
 
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http://www.sqltrainingonline.com SQL Null or Empty - How to Check for Null or Empty Column in SQL Server - SQL Training Online You can download the sample table script at http://www.sqltrainingonline.com/how-to-filter-for-sql-null-or-empty-string/. In this video, I show you how to filter for a SQL null or empty string. It can be difficult to filter a null because you can't simply compare with an equal sign. You have to use a special IS NULL clause to make the filter work. I also show you how to combine both the SQL Null and Empty String together in a special trick with the isnull SQL Server function. I use SQL Server 2012 to demonstrate the technique. Let me know what you think by commenting or sharing on twitter, facebook, google+, etc. If you enjoy the video, please give it a like, comment, or subscribe to my channel. You can visit me at any of the following: SQL Training Online: http://www.sqltrainingonline.com Twitter: http://www.twitter.com/sql_by_joey Google+: https://plus.google.com/#100925239624117719658/posts LinkedIn: http://www.linkedin.com/in/joeyblue Facebook: http://www.facebook.com/sqltrainingonline
Views: 19745 Joey Blue
Database - foreign key option: SET NULL
 
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Demostració del comportament foreign key "set null" en la clausula delete.
Views: 192 Miquel Boada
auto increment in sql oracle - ( Auto increment field )
 
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auto increment in sql oracle ----------------------------------------------- CREATE table customers ( customer_id int not null, customer_name varchar(50), primary key (customer_id) ); create sequence customer_id minvalue 1 start with 1 cache 10; insert into customers values(customer_id.nextval,'maxwel'); -- to drop sequence drop sequence customer_id
Views: 9789 Data Disc
NULL values in DBMS...how to insert null value in table in sql
 
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how to insert null value in table in sql #sqltutorial#oracletutorial#databasetutorial
Views: 1992 Viral Fun Tube
The SQL UPDATE Statement
 
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This video tutorial covers how to update fields in a SQL database table, using the SQL UPDATE statement. More guides and tutorials: http://www.itgeared.com/.
Views: 35354 itgeared
How to Create Foreign Key Constraint with ON DELETE SET NULL Option in SQL Server -SQL Server P81
 
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SQL Server / T-SQL Tutorial Scenario: You are working as SQL Server developer, you need to create two tables with Primary -Foreign Key Relationship. You want to create Foreign Key Constraint with setting if record will be deleted from Referenced Table (Primary Key Column Table), it should not be deleted from Parent Table ( Foreign Key Constraint Table) instead the value should be updated to Null. Link to scripts used in SQL Server / TSQL Tutorial Video http://www.techbrothersit.com/2016/04/how-to-create-foreign-key-constraint_95.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: 1020 TechBrothersIT
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: 26781 Caleb Curry
How TO DELETE ROW, MODIFY, UPDATE COLUMN, DROP TABLE in Oracle SQL Using Cmd [Hindi/Urdu].
 
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Hi Friends !!!!! In this Video we show the How to delete table, row, update etc. Oracle Databse- a) Open The Sqlplus. b) Connect The Workspace. c) Show Your Tables. Query : Select * from tab; d) Select the table where you want to delete row. Query : Delete From [Table Name] Where id=?; e) Show Your Tables. Query : Select * from tab; 1 row delete sucessfully. f) If You Modify Your Table to follow this Query : Alter table [Table Name] modify [Column Name] varchar2(10); Your table column is modified. g) If You Update row data follow this Query Update [Table Name] set [Column Name]='row data of column' where id=?; If you delete the table follow the Query : Drop Table [Table Name]; Your table is deleted sucessfully. Related video Links : How to Install Java Netbeans IDE in Windows 7, 8.1, 10 [Hindi/Urdu]: https://youtu.be/jOYMNognZXM How To Install Java On Window 10, 8.1, 7 64 bit Operating System [Hindi/Urdu] : https://youtu.be/y2-g09nY33A How to install Windows 7, 8.1,10 from a flash drive or Pandrive . [Hindi/Urdu] : https://youtu.be/s4kNcirxWrc How to Make Bootable Your Pandrive [Hindi/Urdu] : https://youtu.be/BPx_Ua_aCfY How to install Oracle 11G XE On Windows 10, 8.1, 7 Operating System in [Hindi/Urdu] : https://youtu.be/-2k4QCIpIOs How to Create Table Oracle Datbase Using Sqlplus [Hindi/Urdu] : https://youtu.be/EHnAebRP6Yw How To Insert Table Oracle Database Using Sqlplus [Hindi/Urdu]: https://youtu.be/Fu0tlCml8F8 How TO DELETE ROW, MODIFY, UPDATE COLUMN, DROP TABLE in Oracle SQL Using Cmd [Hindi/Urdu]: https://youtu.be/prz9Pr0PFEg How to recover format or delete Pandrive, Sdcard, Memory Card Or Harddisk Data [Hindi/Urdu] : https://youtu.be/0GGDHVTxDh0 How to install Oracle SQl Developer And How to Connect Your Database Sql Developer[Hindi/Urdu] : https://youtu.be/608nx3mT10c How to use SQL Distinct Keyword in Cmd Or Oracle SQL Developer [Hindi/Urdu] : https://youtu.be/ofLLZ9-EG_E How to use SQL AND Or OR operator [Hindi/Urdu] : https://youtu.be/zzqDp7U3rC8 How To Use SQL Where Operation using CMD [Hindi/Urdu] : https://youtu.be/EHmL0Wa14UY How To Use SQL ASC and DESC Operation using cmd [Hindi/Urdu] : https://youtu.be/UI0hat_RMX0 For Any Query Email Add : [email protected] Facebook Page link : https://www.facebook.com/Technical-Education-4-You-144220269545756/?ref=nf&hc_ref=ART3p2EX_iIdZHm96Uz36P99q7xfycGfo54RJafY-f0O4n1bdvWU_5xGHpPrOpLepi4
Oracle SQL Tutorial 21 - How to Create / Drop Indexes
 
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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: 10133 Caleb Curry
Oracle PL SQL interview question NULL and Arithmetic operation
 
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Oracle PL SQL interview question NULL and Arithmetic operation Click here to subscribe to my youtube channel http://www.youtube.com/channel/UCBt6VrxAIb5jLh9HLDcdwtQ?sub_confirmation=1 Oracle Interview questions and Answers at https://www.youtube.com/playlist?list=PLb1qVSx1k1Vr0v4wVyvT3GEuA0J0M4xBm Oracle 18C New features at https://www.youtube.com/playlist?list=PLb1qVSx1k1Vqe06V1tIBcvnslMPWX69bW Oracle 12C New features at https://www.youtube.com/playlist?list=PLb1qVSx1k1VqM1u2IHWzZIgziqejl6wx- Oracle PLSQL records and collections at https://www.youtube.com/playlist?list=PLb1qVSx1k1VpAFTXopXvAh_D3PLcTntdm
Views: 787 Siva Academy
What is NULL ? in Oracle SQL
 
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In This Course you will learn how to download oracle and install on mac and window in this course topics will covers as Sql Developer Download , Set up connection in SQL Developer , Create a new user , use sample database , Setting up sample database How to view Data with select statment , selecting indiviual columns Filtering Data with Where in Sql Comparision operators Filtering on Partial values with likes , Filter on data values , using two filters What is Null , Getting Unique Records with DISTINCT , What is IN and NOT in oracle , What is between and not between , All keywords which are used in sql , any keyword , sorting result with order by clause , ordering by Multiple columns ,set operation and union , union all operator , insert operator , Minus oprator , three or more sets at once , what are function in oracle , what is data counting , using count in other ways , Counting Data within groups with Group by Group by having clause , The sum function in sql , the avg function in sql What are table alias , what are column alias , what are joins , inner joins What is left join , gight join , outer join , natural join , cartesian and cross join self join , join many tables , alternative join syntax ,string function , nesting function within functions , number function , data function ,data type and conversion , the case statement what are subquries , single row subquries , multirow subquries , inserting data , inserting from another tables , updating data , Deleting data , Commit and Rollback , truncating data Create a table , alter a table drop a table conclusion
Views: 0 Education
MySQL 33 - Datetime, Date, Time Data Types
 
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Next up on our MySQL to-do list is to learn about storing dates and times. There are various data types in MySQL for storing dates and times. It seems MySQL and databases likes to break everything up into multiple data types to make things more organized at the consequence of being confusing and annoying. This video is going to be talking about the DATETIME, DATE, and TIME data types. These are all used to store, you guessed it, dates and times. The one you choose depends on your needs. If you just need dates, choose DATE. If you just need times, choose TIME, if you need both stored together, choose DATETIME. Now you set a column one of these data types whenever you want every row for this field to have some sort of date, time or both…but how exactly is the data formatted? This requires us to understand some convention. For example, in the USA at least, if you have something like 4:30AM, by convention you know the hour is 4 and the minutes are 30. But this is just an agreed upon convention. MySQL has its own convention…For example 2017-02-02. The first thing is the year, the second is the month, and the third is the day. That is for the DATE. The convention for time is 22:54:30. The first is the hour (military time), the second is the minute, and the third is the seconds. Lastly, there can actually be fractions of seconds…up to microseconds! .123456. To use fractional seconds though you must specify to MySQL the precision of the TIME or DATETIME when you create it, for example DATETIME(6) would allow microsecond precision. How do you actually give a date to MySQL? By that I mean let's say you have a table with a column of DATETIME(6), and you want to give a value for that column, how do you format it? It's quoted. For example: '2017-02-02 22:54:30.333333' MySQL interprets this as a DATETIME. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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: 40649 Caleb Curry
MySQL - Insert Null in Database
 
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Get Source Code/Read : http://intactabode.com/ For Developing support email your Details at : [email protected] Install Free Trail GST Ready Accounting Package Send your Contact information Name, Email, Contact Number to watch demo in English : https://www.youtube.com/watch?v=a4sFNtZuYzs&ab_channel=IntactAbode watch demo in Hindi : https://www.youtube.com/watch?v=I3eCieDpG3o&ab_channel=IntactAbode For Source Code Visit : http://corneey.com/wJ6X2K Subscribe to YouTube channel http://corneey.com/wJ6VoC Like us on Facebook http://corneey.com/wJ6C2l Follow us on Twitter http://corneey.com/wJ6C7x Follow me on Google+ http://corneey.com/wJ6Vhc linkedin http://corneey.com/wJ6V5g Watch More Frequently Used Sql Queries in all Databases Complete Playlist: https://www.youtube.com/playlist?list=PLErD1cRL87W992bgZ_TX7gxl5UKuP9yF9 how to insert null value in mysql how to update null value in sql how to insert null value in sql using c# how to insert null value in sql server 2008 sql insert null date how to insert null value in oracle how to insert null value in integer field in sql server how to insert blank value in sql
Views: 2698 Intact Abode
ADD ROW by using INSERT INTO and having one NULL value,
 
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I am inserting a new row with my information and giving my cell phone number as a null value. Afterwards I use the DELETE statement to remove the row I added
Views: 1432 Roger Perez
The Magic of SQL: Column Update Mystery
 
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You use the update statement in SQL to modify existing values in a row. Normally you have to assign values to each column explicitly. In this video Chris updates the value in one column and also changes the value in another column - without any triggers in sight! Watch the video to see how it's done! ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 6591 The Magic of SQL
Part 4   Delete duplicate rows in sql
 
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Link for all dot net and sql server video tutorial playlists http://www.youtube.com/user/kudvenkat/playlists Link for slides, code samples and text version of the video http://csharp-video-tutorials.blogspot.com/2014/05/part-4-delete-duplicate-rows-in-sql.html In this video, we will discuss deleting all duplicate rows except one from a sql server table. SQL Script to create Employees table Create table Employees ( ID int, FirstName nvarchar(50), LastName nvarchar(50), Gender nvarchar(50), Salary int ) GO Insert into Employees values (1, 'Mark', 'Hastings', 'Male', 60000) Insert into Employees values (1, 'Mark', 'Hastings', 'Male', 60000) Insert into Employees values (1, 'Mark', 'Hastings', 'Male', 60000) Insert into Employees values (2, 'Mary', 'Lambeth', 'Female', 30000) Insert into Employees values (2, 'Mary', 'Lambeth', 'Female', 30000) Insert into Employees values (3, 'Ben', 'Hoskins', 'Male', 70000) Insert into Employees values (3, 'Ben', 'Hoskins', 'Male', 70000) Insert into Employees values (3, 'Ben', 'Hoskins', 'Male', 70000) The delete query should delete all duplicate rows except one. Here is the SQL query that does the job. PARTITION BY divides the query result set into partitions. WITH EmployeesCTE AS ( SELECT *, ROW_NUMBER()OVER(PARTITION BY ID ORDER BY ID) AS RowNumber FROM Employees ) DELETE FROM EmployeesCTE WHERE RowNumber ] 1
Views: 364754 kudvenkat
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: 104206 Manish Sharma
Java prog#14.How to Insert/Save data from netbeans java into database Sqlite (MySql)
 
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------------------Online Courses to learn---------------------------- Java - https://bit.ly/2H6wqXk C++ - https://bit.ly/2q8VWl1 AngularJS - https://bit.ly/2qebsLu Python - https://bit.ly/2Eq0VSt C- https://bit.ly/2HfZ6L8 Android - https://bit.ly/2qaRSAS Linux - https://bit.ly/2IwOuqz AWS Certified Solutions Architect - https://bit.ly/2JrGoAF Modern React with Redux - https://bit.ly/2H6wDtA MySQL - https://bit.ly/2qcF63Z ----------------------Follow--------------------------------------------- My Website - http://www.codebind.com My Blog - https://goo.gl/Nd2pFn My Facebook Page - https://goo.gl/eLp2cQ Google+ - https://goo.gl/lvC5FX Twitter - https://twitter.com/ProgrammingKnow Pinterest - https://goo.gl/kCInUp Text Case Converter - https://goo.gl/pVpcwL -------------------------Stuff I use to make videos ------------------- Stuff I use to make videos Windows notebook – http://amzn.to/2zcXPyF Apple MacBook Pro – http://amzn.to/2BTJBZ7 Ubuntu notebook - https://amzn.to/2GE4giY Desktop - http://amzn.to/2zct252 Microphone – http://amzn.to/2zcYbW1 notebook mouse – http://amzn.to/2BVs4Q3 ------------------Facebook Links ---------------------------------------- http://fb.me/ProgrammingKnowledgeLearning/ http://fb.me/AndroidTutorialsForBeginners http://fb.me/Programmingknowledge http://fb.me/CppProgrammingLanguage http://fb.me/JavaTutorialsAndCode http://fb.me/SQLiteTutorial http://fb.me/UbuntuLinuxTutorials http://fb.me/EasyOnlineConverter netbeans java tutorial how to insert data from netbeans into database Insert information into a MySQL database - NetBeans - Java Insert Data Into Mysql Database Using Netbeans Insert Data Of Textfields In Database "netbeans"‎ Insert Data Into Database Using Netbeans to insert, update and delete new data into mysql database using jbutton. How to insert data into database how to insert java.sql.data into database sql - Java Date - Insert into database How to Insert Data into a table in mysql database insert values in table,JDBC Insert Row JDBC program to insert data into mysql database from java netbeans iit Learn java netbeans java tutorial netbeans
Views: 191766 ProgrammingKnowledge
SQL Tutorial - The UPDATE Query # The SQL UPDATE Statement
 
05:22
Learn .net , android , c , c++ , php , java from androidatpoint.co.in
Views: 22 Abhishek Tripathi
Dynamic SQL in Stored Procedure
 
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In this video we will discuss, using dynamic sql in a stored procedure and it's implications from sql injection perspective. We will discuss performance implications of using dynamic sql in a stored procedure in a later video. Text version of the video http://csharp-video-tutorials.blogspot.com/2017/04/dynamic-sql-in-stored-procedure.html Slides http://csharp-video-tutorials.blogspot.com/2017/04/dynamic-sql-in-stored-procedure_11.html All SQL Server Text Articles http://csharp-video-tutorials.blogspot.com/p/free-sql-server-video-tutorials-for.html All SQL Server Slides http://csharp-video-tutorials.blogspot.com/p/sql-server.html All SQL Server Tutorial Videos https://www.youtube.com/playlist?list=PL08903FB7ACA1C2FB All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists Consider the following stored procedure "spSearchEmployees". We implemented this procedure in Part 139 of SQL Server tutorial. This stored procedure does not have any dynamic sql in it. It is all static sql and is immune to sql injection. Create Procedure spSearchEmployees @FirstName nvarchar(100) = NULL, @LastName nvarchar(100) = NULL, @Gender nvarchar(50) = NULL, @Salary int = NULL As Begin Select * from Employees where (FirstName = @FirstName OR @FirstName IS NULL) AND (LastName = @LastName OR @LastName IS NULL) AND (Gender = @Gender OR @Gender IS NULL) AND (Salary = @Salary OR @Salary IS NULL) End Go Whether you are creating your dynamic sql queries in a client application like ASP.NET web application or in a stored procedure, you should never ever concatenate user input values. Instead you should be using parameters. Notice in the following example, we are creating dynamic sql queries by concatenating parameter values, instead of using parameterized queries. This stored procedure is prone to SQL injection. Let's prove this by creating a "Search Page" that calls this procedure. Create Procedure spSearchEmployeesBadDynamicSQL @FirstName nvarchar(100) = NULL, @LastName nvarchar(100) = NULL, @Gender nvarchar(50) = NULL, @Salary int = NULL As Begin Declare @sql nvarchar(max) Set @sql = 'Select * from Employees where 1 = 1' if(@FirstName is not null) Set @sql = @sql + ' and FirstName=''' + @FirstName + '''' if(@LastName is not null) Set @sql = @sql + ' and LastName=''' + @LastName + '''' if(@Gender is not null) Set @sql = @sql + ' and Gender=''' + @Gender + '''' if(@Salary is not null) Set @sql = @sql + ' and Salary=''' + @Salary + '''' Execute sp_executesql @sql End Go Add a Web Page to the project that we have been working with in our previous video. Name it "DynamicSQLInStoredProcedure.aspx". Copy and paste the HTML and code available on my blog at the following link http://csharp-video-tutorials.blogspot.com/2017/04/dynamic-sql-in-stored-procedure.html At this point, run the application and type the following text in the "Firsname" text and click "Search" button. Notice "SalesDB" database is dropped. Our application is prone to SQL injection as we have implemented dynamic sql in our stored procedure by concatenating strings instead of using parameters. ' Drop database SalesDB -- In the following stored procedure we have implemented dynamic sql by using parameters, so this is not prone to sql injecttion. This is an example for good dynamic sql implementation. Create Procedure spSearchEmployeesGoodDynamicSQL @FirstName nvarchar(100) = NULL, @LastName nvarchar(100) = NULL, @Gender nvarchar(50) = NULL, @Salary int = NULL As Begin Declare @sql nvarchar(max) Declare @sqlParams nvarchar(max) Set @sql = 'Select * from Employees where 1 = 1' if(@FirstName is not null) Set @sql = @sql + ' and [email protected]' if(@LastName is not null) Set @sql = @sql + ' and [email protected]' if(@Gender is not null) Set @sql = @sql + ' and [email protected]' if(@Salary is not null) Set @sql = @sql + ' and [email protected]' Execute sp_executesql @sql, N'@FN nvarchar(50), @LN nvarchar(50), @Gen nvarchar(50), @sal int', @[email protected], @[email protected], @[email protected], @[email protected] End Go On the code-behind page, use stored procedure spSearchEmployeesGoodDynamicSQL instead of spSearchEmployeesBadDynamicSQL. We do not have to change any other code. At this point run the application one more time and type the following text in the "Firstname" textbox and click the "Search" button. ' Drop database SalesDB -- Notice "SalesDB" database is not dropped, So in this case our application is not succeptible to SQL injection attack. Summary : Whether you are creating dynamic sql in a client application (like a web application) or in a stored procedure always use parameters instead of concatnating strings. Using parameters to create dynamic sql statements prevents sql injection.
Views: 38018 kudvenkat
MySQL Database Tutorial - 27 - How to Insert Multiple Rows
 
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Facebook - https://www.facebook.com/TheNewBoston-464114846956315/ GitHub - https://github.com/buckyroberts Google+ - https://plus.google.com/+BuckyRoberts LinkedIn - https://www.linkedin.com/in/buckyroberts reddit - https://www.reddit.com/r/thenewboston/ Support - https://www.patreon.com/thenewboston thenewboston - https://thenewboston.com/ Twitter - https://twitter.com/bucky_roberts
Views: 113289 thenewboston
HeidiSQL - Insert NULL values on data grid
 
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To insert a NULL value on the HeidiSQL datagrid: 1. select a column with NULL data 2. Copy the NULL data 3. Paste the NULL data as many times as you want
Views: 2177 Webspicer
Oracle Drop, Disable and Enable Constraints تعليم اوراكل
 
09:35
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
Learn MySQL In Arabic #18 - Constraint - Foreign Key Update, Delete
 
14:22
Learn Foreign Key Options OnUpdate and OnDelete Cascade | Restrict | Set Null | No Action
Views: 12441 Elzero Web School
MySQL - How to Change Null Values to 0 in SQL
 
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Get Source Code/Read : http://intactabode.com/ For Developing support email your Details at : [email protected] Install Free Trail GST Ready Accounting Package Send your Contact information Name, Email, Contact Number to email : [email protected] watch demo in English : https://www.youtube.com/watch?v=a4sFNtZuYzs&ab_channel=IntactAbode watch demo in Hindi : https://www.youtube.com/watch?v=I3eCieDpG3o&ab_channel=IntactAbode Website : http://relybill.com/ Watch More Frequently Used Sql Queries in all Databases Complete Playlist: https://www.youtube.com/playlist?list=PLErD1cRL87W992bgZ_TX7gxl5UKuP9yF9 In this videos i show how to update your null values to zero or o in sql, if you wanted change all the null values in your sql to numerical zero 0, this syntax will sure help you to solve the problem. in some cases i you wanted to display your null values to 0 in sql, mysql, oracle or any other jdbc database this querry will sure help you solve the problem in sql syntax. For Source Code Visit : http://corneey.com/wJ6X2K Subscribe to YouTube channel http://corneey.com/wJ6VoC Like us on Facebook http://corneey.com/wJ6C2l Follow us on Twitter http://corneey.com/wJ6C7x Follow me on Google+ http://corneey.com/wJ6Vhc linkedin http://corneey.com/wJ6V5g
Views: 3238 Intact Abode
Oracle Database | Bangla Tutorials 23 :: Constraint Not null
 
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www.facebook.com/oracle.shohag Email : [email protected] Website : www.oraclebangla.com Topics : Constraint Not null
Views: 1049 Oracle Bangla
Learn Oracle | How to Create a Table using SQL | Not Null, Unique Key, Primary Key
 
14:50
Pebbles present, Learn Oracle 10g with Step By Step Video Tutorials. Learn Oracle 10g Tutorial series contains the following videos : Learn Oracle - History of Oracle Learn Oracle - What is Oracle - Why do we need Oracle Learn Oracle - What is a Database Learn Oracle - What is Grid Computing Learn Oracle - What is Normalization Learn Oracle - What is ORDBMS Learn Oracle - What is RDBMS Learn Oracle - Alias Names, Concatenation, Distinct Keyword Learn Oracle - Controlling and Managing User Access (Data Control Language) Learn Oracle - Introduction to SQL Learn Oracle - Oracle 10g New Data Types Learn Oracle - How to Alter a Table using SQL Learn Oracle - How to Create a Package in PL SQL Learn Oracle - How to Create a Report in SQL Plus Learn Oracle - How to Create a Table using SQL - Not Null, Unique Key, Primary Key Learn Oracle - How to Create a Table using SQL Learn Oracle - How to Create a Trigger in PL SQL Learn Oracle - How to Delete Data from a Table using SQL Learn Oracle - How to Drop and Truncate a Table using SQL Learn Oracle - How to Insert Data in a Table using SQL Learn Oracle - How to open ISQL Plus for the first time Learn Oracle - How to Open SQL Plus for the First Time Learn Oracle - How to Update a Table using SQL Learn Oracle - How to use Aggregate Functions in SQL Learn Oracle - How to use Functions in PL SQL Learn Oracle - How to use Group By, Having Clause in SQL Learn Oracle - How to Use Joins, Cross Join, Cartesian Product in SQL Learn Oracle - How to use Outer Joins (Left, Right, Full) in SQL Learn Oracle - How to use the Character Functions, Date Functions in SQL Learn Oracle - How to use the Merge Statement in SQL Learn Oracle - How to use the ORDER BY Clause with the Select Statement Learn Oracle - How to use the SELECT Statement Learn Oracle - How to use the Transactional Control Statements in SQL Learn Oracle - How to use PL SQL Learn Oracle - Data Types in PL SQL Learn Oracle - Exception Handling in PL SQL Learn Oracle - PL SQL Conditional Logics Learn Oracle - PL SQL Cursor Types - Explicit Cursor, Implicit Cursor Learn Oracle - PL SQL Loops Learn Oracle - Procedure Creation in PL SQL Learn Oracle - Select Statement with WHERE Cause Learn Oracle - SQL Operators and their Precedence Learn Oracle - Using Case Function, Decode Function in SQL Learn Oracle - Using Logical Operators in the WHERE Clause of the Select Statement Learn Oracle - Using Rollup Function, Cube Function Learn Oracle - Using Set Operators in SQL Learn Oracle - What are the Different SQL Data Types Learn Oracle - What are the different types of Databases Visit Pebbles Official Website - http://www.pebbles.in Subscribe to our Channel – https://www.youtube.com/channel/UCNNjWVsQqaMYccY044vtHJw?sub_confirmation=1 Engage with us on Facebook at https://www.facebook.com/PebblesChennai Please Like, Share, Comment & Subscribe
Views: 201 Pebbles Tutorials
SQL,  How to insert date data type, lesson 14
 
08:23
14th video of the series, learning structured Query Language. How to insert date data type into a column. Using oracle platform.
Views: 46331 hammadshams
Adding Not Null to an Existing Column
 
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In this episode, I'm going to add a not null constraint to an existing Postgres column. To learn more and for full transcript visit us at https://www.pgcasts.com This episode is sponsored by Hashrocket, a consultancy specializing in PostgreSQL. Visit us at https://hashrocket.com
Views: 2063 PG Casts
Cascading referential integrity constraint in SQL Server- PART 5
 
20:09
We tried to explain Cascading Referential Integrity, please like, share and subscribe: Please refer to the definition below: The Foreign Key constraint enforces referential integrity by guaranteeing that changes cannot be made to data in the primary key table if those changes invalidate the link to data in the foreign key table. If an attempt is made to delete the row in a primary key table or to change a primary key value, the action will fail when the deleted or changed primary key value corresponds to a value in the FOREIGN KEY constraint of another table. To successfully change or delete a row in a FOREIGN KEY constraint, you must first either delete the foreign key data in the foreign key table or change the foreign key data in the foreign key table, which links the foreign key to different primary key data. Syntax: The REFERENCES clauses of the CREATE TABLE statements support the ON DELETE and ON UPDATE classes: -ON DELETE (NO ACTION CASCADE I SET NULL I SET DEFAULT) -ON UPDATE (NO ACTION I CASCADE I SET NULL I SET DEFAULT)