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Dropping a constraint, key, or index

To drop a CHECK constraint, you need to run the following query:

USE foraltering;ALTER TABLE tableforalteringDROP CHECK check_yearID;

The preceding query drops the CHECK constraint named check_yearID. Dropping CHECK constraints is different from dropping other constraints, such as foreign keys or primary keys. A foreign key constraint can be dropped using the following query:

ALTER TABLE tablenameDROP FOREIGN KEY FK_keyname;

Primary key constraints can be dropped using the following query:

ALTER TABLE tablenameDROP PRIMARY KEY;

An index can be dropped using the following query:

USE yourschema;ALTER TABLE managers DROP INDEX playerID_yearID_teamID_UNIQUE;

There are some differences in dropping constraints ...