MySQL LAST_INSERT_ID() used with multiple records INSERT statement

Question

If I insert multiple records with a loop that executes a single record insert, the last insert id returned is, as expected, the last one. But if I do a multiple records insert statement:

INSERT INTO people (name,age) VALUES ('William',25), ('Bart',15), ('Mary',12); 

Let's say the three above are the first records inserted in the table. After the insert statement I expected the last insert id to return 3, but it returned 1. The first insert id for the statement in question.

So can someone please confirm if this is the normal behavior of LAST_INSERT_ID() in the context of multiple records INSERT statements. So I can base my code on it.

Answer 1

Yes. This behavior of last_insert_id() is documented in the MySQL docs:

Important
If you insert multiple rows using a single INSERT statement, LAST_INSERT_ID() returns the value generated for the first inserted row only. The reason for this is to make it possible to reproduce easily the same INSERT statement against some other server.

Answer 2

This behavior is mentioned on the man page for MySQL. It's in the comments but is not challenged, so I'm guessing it's the expected behavior.