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SQL Blogsby Rudy1 min3,370

Adding Foreign Keys after a table is created in SQL Server

Well, you knew exactly what you needed when you created a table. Only now when you created a child table, the child table does not update with the information from your main table. Or worse you deleted something from your primary table and it still lives in the child table. You need a foreign key, my friend. This is how you define one after you’ve created your table. ALTER TABLE My_Child_Table ADD CONSTRAINT FK_User_ID FOREIGN KEY ( User_ID_In_Child_Table ) REFERENCES My_Primary_Table ( User_ID_In_Primary_Table ) ON DELETE CASCADE ON UPDATE CASCADE The last two lines are important. In this example, if … Continue reading Adding Foreign Keys after a table is created in SQL Server

Programmingby Rudy1 min1,549

Adding Checks after a table is created in SQL Server

Did you create a table, only to find that you need to add a check constraint? I created a quick example of how to add a check constraint after the table exists. In this example, we want to know if our user is alive or dead. 1 = alive, 0 = dead. Here is the code for SQL server: alter table dbo.Tbl_User_Table add constraint CK_User_Alive check (User_Alive in (0,1)) I don’t know if it will work with MySql, Oracle, etc, so check your documentation. Happy Coding! RudyRudy Rodarte is a SQL Server Database professional based in Austin, TX. Over his … Continue reading Adding Checks after a table is created in SQL Server