InnoDB Locking on MySQL

https://dev.mysql.com/doc/refman/5.5/en/innodb-locking.html This section describes lock types used by InnoDB. Shared and Exclusive Locks, Intention Locks, Record Locks, Gap Locks, Next-Key Locks, Insert Intention Locks, AUTO-INC Locks Shared and Exclusive Locks InnoDB implements standard row-level locking where there are two types of locks, shared (S) locks and exclusive (X) locks.