How to Delete/Drop a Constraint In PostgresSQL

This article will show you how to drop a constraint, such as a foreign key constraint, on a PostgresSQL database. There are several different types of constraints and we’ll show you examples of each.

Sure, here are the same instructions with headers and sub-headers:

Dropping a PRIMARY KEY Constraint in PostgreSQL

To remove a primary key constraint, use the following syntax:

SQL Command:

ALTER TABLE table_name DROP CONSTRAINT table_name_pkey;

Replace “table_name” and “table_name_pkey” with your actual table name and primary key constraint name respectively.

Dropping a FOREIGN KEY Constraint

If you wish to drop a foreign key constraint, use this command:

SQL Command:

ALTER TABLE table_name DROP CONSTRAINT foreign_key_name;

Here, replace “table_name” and “foreign_key_name” with your actual table name and foreign key constraint name respectively.

Dropping a UNIQUE Constraint

To drop a unique constraint, use the following syntax:

SQL Command:

ALTER TABLE table_name DROP CONSTRAINT unique_constraint_name;

In this command, replace “table_name” and “unique_constraint_name” with your actual table name and unique constraint name respectively.

Dropping a CHECK Constraint

To remove a check constraint, use this command:

SQL Command:

ALTER TABLE table_name DROP CONSTRAINT check_constraint_name;

Ensure to replace “table_name” and “check_constraint_name” with your actual table name and check constraint name respectively.

Dropping a NOT NULL Constraint

To drop a NOT NULL constraint, use the following command:

SQL Command:

ALTER TABLE table_name ALTER COLUMN column_name DROP NOT NULL;

Replace “table_name” and “column_name” with your actual table name and column name respectively. This will remove the NOT NULL constraint from the specified column.