DROP CONSTRAINT
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.
See also
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