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

Synopsis

ALTER TABLE IF EXISTS table_name DROP CONSTRAINT IF EXISTS name

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.

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

See Also



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