MySQL in a Nutshell, 2nd Edition

Name

GET_LOCK()

Synopsis

GET_LOCK(string, seconds)

This function attempts to get a lock on the name given in the first argument. The number of seconds to attempt the lock is given in the second argument. If successful, it returns 1. If the function is unsuccessful because the attempt times out, it returns 0. If the lock fails due to an error of any kind, NULL is returned. The function RELEASE_LOCK() may be used to release a lock. A lock is also released when the same client issues another GET_LOCK() or when the client’s connection is terminated. Here is an example:

SELECT GET_LOCK('my_lock', 10);

+-------------------------+
| GET_LOCK('my_lock', 10) |
+-------------------------+
|                       1 |
+-------------------------+