Mysql obtains the value of the auto-increment field in the table.

INSERT multiple records using a single INSERT statement. LAST_INSERT_ID only returns the value of the first inserted record. For example:

1. mysql> insert into t VALUES (NULL, 'aaa'), (NULL, 'bbbbbb'), (NULL, 'cccccc ');
2. mysql> SELECT * FROM t;
3. + ---- + ------ +
4. | id | name |
5. + ---- + ------ +
6. | 1 | Bob |
7. | 2 | aaaa |
8. | 3 | bbbb |
9. | 4 | cccc |
10. + ---- + ------ +
11. mysql> SELECT LAST_INSERT_ID ();
12. + ------------------ +
13. | LAST_INSERT_ID () |
14. + ------------------ +
15. | 2 |
16. + ------------------ +

ID 2 is generated when the first record aaaa is inserted.

LAST_INSERT_ID is table-independent. If you insert data to table a and then insert data to table B, LAST_INSERT_ID will change.

Generally, you can obtain the id of the inserted data by using select max (id) from table.

But in the case of multiple threads, it won't work. Max (id) is obviously unavailable when multiple users insert data alternately.

This
LAST_INSERT_ID should be used, because LAST_INSERT_ID is based on Connection, as long as each thread uses an independent
Connection object. The LAST_INSERT_ID function returns the latest insert or
The ID of the first record generated by the update operation. This value cannot be affected by other clients (connections), so that you can retrieve your ID.
You don't have to worry about the activities of other clients, and do not need to lock them.