SQL CONSTRAINT Keyword

CONSTRAINT Keyword

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Add Constraint

The ADD CONSTRAINT

Example

ALTER TABLE Persons

ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName);

Drop Constraint

The DROP CONSTRAINT

DROP a UNIQUE Constraint

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

SQL Server / Oracle / MS Access:

ALTER TABLE Persons

DROP CONSTRAINT PK_Person;

MySQL:

ALTER TABLE Persons

DROP PRIMARY KEY;

DROP a FOREIGN KEY Constraint

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

SQL Server / Oracle / MS Access:

ALTER TABLE Persons

DROP CONSTRAINT CHK_PersonAge;

MySQL: