constraint Archives - Gullele's Corner

postgres not null to null

How to remove NOT NULL constraint in postgres

A NOT NULL constraint is essential tool in postgres database to ensure validation.

But sometimes, you need to remove not null and allow column to be null.

Remove NOT NULL Postgres


ALTER TABLE table_name ALTER COLUMN column_name DROP NOT NULL

Cannot truncate a table referenced in a foreign key constraint mysql error

Trying to update the schema or truncating the table or something else and got this error?
Turn the constraint temporarily and the issue shall be fixed:

SET FOREIGN_KEY_CHECKES=0;
TRUNCATE TABLE somepoortable;
.
.
SET FOREIGN_KEY_CHECKS=1;

That is it!

Constraints in SQL Server

A good examples on constraints can be found here:

http://www.mssqlcity.com/Articles/General/using_constraints.htm