Drop Constraint
The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint.
DROP a UNIQUE Constraint
To drop a UNIQUE constraint, use the following SQL:
SQL Server / Oracle / MS Access:
ALTER TABLE Persons
DROP CONSTRAINT UC_Person;MySQL
ALTER TABLE Persons
DROP INDEX UC_Person;DROP a PRIMARY KEY Constraint
To drop a PRIMARY KEY constraint, use the following SQL:
SQL Server / Oracle / MS Access:
ALTER TABLE Persons
DROP CONSTRAINT PK_Person;MySQL
ALTER TABLE Persons
DROP PRIMARY KEY;DROP a FOREIGN KEY Constraint
To drop a FOREIGN KEY constraint, use the following SQL:
SQL Server / Oracle / MS Access:
ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;MySQL
ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;DROP a CHECK Constraint
To drop a CHECK constraint, use the following SQL:
SQL Server / Oracle / MS Access:
ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;MySQL
ALTER TABLE Persons
DROP CHECK CHK_PersonAge;