Discussion Board

Foreign key The above statement is wrong. A foreign key column must not contain unique values. A FOREIGN KEY constraint can contain null values; however, if any column of a composite FOREIGN KEY constraint contains null values, verification of all values that make up the FOREIGN KEY constraint is skipped. To make sure that all values of a composite FOREIGN KEY constraint are verified, specify NOT NULL on all the participating columns. A foreign key (FK) is a column or combination of columns that is used to establish and enforce a link between the data in two tables. You can create a foreign key by defining a FOREIGN KEY constraint when you create or modify a table. Prajakta Pandit 02-2-2017 06:37 AM

Write your comments

*

* Email must be in the form someone@domain.com

*

*