Re: NOLOCK for multiple tables

[Øystein Grøvlen]

Hi,

AFAIK, NOLOCK clause is not supported in MySQL.

Note that what kind of locking is used will depend on the storage engine.

For isolation level READ COMMITTED, InnoDB will not acquire any locks for SELECT statements. It uses Multiversion Concurrency Control (MVCC) and will read the versions at the time when the execution of the query started. For REPEATABLE READ, so-called gap locks will be used to prevent phantoms. Gap locks will make sure that no new records will be inserted into the range that was accessed by the query.

Regards,

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway