DROP CONSTRAINT

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The DROP CONSTRAINT statement is part of ALTER TABLE and removes Check and Foreign Key constraints from columns.

Note:

For information about removing other constraints, see Constraints: Remove Constraints.

Tip:

New in v19.1: This command can be combined with other ALTER TABLE commands in a single statement. For a list of commands that can be combined, see ALTER TABLE. For a demonstration, see Add and rename columns atomically.

Synopsis

Required privileges

The user must have the CREATE privilege on the table.

Parameters

Parameter	Description
`table_name`	The name of the table with the constraint you want to drop.
`name`	The name of the constraint you want to drop.

Viewing schema changes

This schema change statement is registered as a job. You can view long-running jobs with SHOW JOBS.

Example

> SHOW CONSTRAINTS FROM orders;

+--------+---------------------------+-------------+-----------+----------------+
| Table  |           Name            |    Type     | Column(s) |    Details     |
+--------+---------------------------+-------------+-----------+----------------+
| orders | fk_customer_ref_customers | FOREIGN KEY | customer  | customers.[id] |
| orders | primary                   | PRIMARY KEY | id        | NULL           |
+--------+---------------------------+-------------+-----------+----------------+

> ALTER TABLE orders DROP CONSTRAINT fk_customer_ref_customers;

ALTER TABLE

> SHOW CONSTRAINTS FROM orders;

+--------+---------+-------------+-----------+---------+
| Table  |  Name   |    Type     | Column(s) | Details |
+--------+---------+-------------+-----------+---------+
| orders | primary | PRIMARY KEY | id        | NULL    |
+--------+---------+-------------+-----------+---------+

Note:

You cannot drop the primary constraint, which indicates your table's Primary Key.

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