How to Unlock Tables in MySQL: Syntax and Examples

To unlock tables in MySQL, use the UNLOCK TABLES command. This releases all table locks held by the current session, allowing other sessions to access those tables again.

Syntax

The UNLOCK TABLES command releases all locks that the current session holds on tables. It does not require any arguments.

Use it after you have locked tables with LOCK TABLES to allow other sessions to access those tables.

sql

UNLOCK TABLES;

Example

This example shows locking a table, performing a simple query, and then unlocking the tables to release the lock.

sql

LOCK TABLES employees WRITE;
-- Perform operations on the employees table
SELECT * FROM employees LIMIT 1;
UNLOCK TABLES;

Output

Query OK, 0 rows affected (0.00 sec)

+----+------------+-----------+
| id | first_name | last_name |
+----+------------+-----------+
|  1 | John       | Doe       |
+----+------------+-----------+

Query OK, 0 rows affected (0.00 sec)

Common Pitfalls

• Forgetting to unlock tables after locking them can cause other sessions to hang waiting for the lock to be released.
• Using UNLOCK TABLES releases all locks for the current session, so you cannot selectively unlock tables.
• Locks are session-specific; unlocking tables in one session does not affect locks held by other sessions.

sql

/* Wrong: Forgetting to unlock tables */
LOCK TABLES employees WRITE;
-- Operations here
-- No UNLOCK TABLES; command

/* Right: Always unlock after locking */
LOCK TABLES employees WRITE;
-- Operations here
UNLOCK TABLES;

Quick Reference

Command	Description
LOCK TABLES table_name [READ|WRITE]	Locks a table for reading or writing.
UNLOCK TABLES	Releases all table locks held by the current session.
SHOW OPEN TABLES	Shows tables that are currently open and locked.
LOCK TABLES ...	Must be followed by UNLOCK TABLES to release locks.

Key Takeaways

Use UNLOCK TABLES to release all locks held by your session.

Always unlock tables after locking to avoid blocking other sessions.

Locks are session-specific and do not affect other sessions.

You cannot unlock individual tables; UNLOCK TABLES releases all locks at once.