SELECT ... FROM is a consistent read, reading a snapshot of the database and setting no locks unless the transaction isolation level is set to SERIALIZABLE. For SERIALIZABLE level, this sets shared next-key locks on the index records it encounters.

SELECT ... FROM ... LOCK IN SHARE MODE sets shared next-key locks on all index records the read encounters.

SELECT ... FROM ... FOR UPDATE sets exclusive next-key locks on all index records the read encounters.

INSERT INTO ... VALUES (...) sets an exclusive lock on the inserted row. Note that this lock is not a next-key lock and does not prevent other users from inserting to the gap before the inserted row. If a duplicate-key error occurs, a shared lock on the duplicate index record is set.

While initializing a previously specified AUTO_INCREMENT column on a table, InnoDB sets an exclusive lock on the end of the index associated with the AUTO_INCREMENT column. In accessing the auto-increment counter, InnoDB uses a specific table lock mode AUTO-INC where the lock lasts only to the end of the current SQL statement, not to the end of the entire transaction. Note that other clients cannot insert into the table while the AUTO-INC table lock is held; see Section 14.2.10.2, “InnoDB and AUTOCOMMIT”.

InnoDB fetches the value of a previously initialized AUTO_INCREMENT column without setting any locks.

INSERT INTO T SELECT ... FROM S WHERE ... sets an exclusive (non-next-key) lock on each row inserted into T. InnoDB sets shared next-key locks locks on S, unless innodb_locks_unsafe_for_binlog is enabled, in which case it does the search on S as a consistent read. InnoDB has to set locks in the latter case: In roll-forward recovery from a backup, every SQL statement has to be executed in exactly the same way it was done originally.

CREATE TABLE ... SELECT ... performs the SELECT as a consistent read or with shared locks, as in the previous item.

REPLACE is done like an insert if there is no collision on a unique key. Otherwise, an exclusive next-key lock is placed on the row that has to be updated.

UPDATE ... WHERE ... sets an exclusive next-key lock on every record the search encounters.

DELETE FROM ... WHERE ... sets an exclusive next-key lock on every record the search encounters.

If a FOREIGN KEY constraint is defined on a table, any insert, update, or delete that requires the constraint condition to be checked sets shared record-level locks on the records that it looks at to check the constraint. InnoDB also sets these locks in the case where the constraint fails.

LOCK TABLES sets table locks, but it is the higher MySQL layer above the InnoDB layer that sets these locks. InnoDB is aware of table locks if innodb_table_locks=1 (the default) and AUTOCOMMIT=0, and the MySQL layer above InnoDB knows about row-level locks. Otherwise, InnoDB's automatic deadlock detection cannot detect deadlocks where such table locks are involved. Also, because the higher MySQL layer does not know about row-level locks, it is possible to get a table lock on a table where another user currently has row-level locks. However, this does not endanger transaction integrity, as discussed in Section 14.2.10.10, “Deadlock Detection and Rollback”. See also Section 14.2.16, “Restrictions on InnoDB Tables”.