MySQL Tutorial/Table/AUTO INCREMENT

For a multiple-row insert, LAST_INSERT_ID() returns the AUTO_INCREMENT key from the first of the inserted rows

mysql>
mysql>
mysql>
mysql> CREATE TABLE employee (
    ->      id MEDIUMINT NOT NULL AUTO_INCREMENT,
    ->      name CHAR(30) NOT NULL,
    ->      PRIMARY KEY (id)
    ->  );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> INSERT INTO employee (name) VALUES ("A"),
    ->                                    ("B"),
    ->                                    ("C"),
    ->                                    ("D"),
    ->                                    ("E"),
    ->                                    ("F");
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0
mysql>
mysql> SELECT * FROM employee;
+----+------+
| id | name |
+----+------+
|  1 | A    |
|  2 | B    |
|  3 | C    |
|  4 | D    |
|  5 | E    |
|  6 | F    |
+----+------+
6 rows in set (0.02 sec)
mysql>
mysql> select LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                1 |
+------------------+
1 row in set (0.00 sec)
mysql>
mysql> drop table employee;
Query OK, 0 rows affected (0.01 sec)
mysql>

To start with an AUTO_INCREMENT value other than 1

mysql>
mysql> CREATE TABLE employee (
    ->      id MEDIUMINT NOT NULL AUTO_INCREMENT,
    ->      name CHAR(30) NOT NULL,
    ->      PRIMARY KEY (id)
    ->  );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> desc employee;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | mediumint(9) | NO   | PRI | NULL    | auto_increment |
| name  | char(30)     | NO   |     |         |                |
+-------+--------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
mysql>
mysql> ALTER TABLE employee AUTO_INCREMENT = 100;
Query OK, 0 rows affected (0.05 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> INSERT INTO employee (name) VALUES ("A"),
    ->                                    ("B"),
    ->                                    ("C"),
    ->                                    ("D"),
    ->                                    ("E"),
    ->                                    ("F");
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0
mysql>
mysql> SELECT * FROM employee;
+-----+------+
| id  | name |
+-----+------+
| 100 | A    |
| 101 | B    |
| 102 | C    |
| 103 | D    |
| 104 | E    |
| 105 | F    |
+-----+------+
6 rows in set (0.00 sec)
mysql>
mysql> select LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|              100 |
+------------------+
1 row in set (0.00 sec)
mysql>
mysql> drop table employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql>

Use Auto_increment column as part of the key

mysql>
mysql> CREATE TABLE employee (
    ->     grp ENUM("A","B","C") NOT NULL,
    ->     id MEDIUMINT NOT NULL AUTO_INCREMENT,
    ->     name CHAR(30) NOT NULL,
    ->     PRIMARY KEY (grp,id)
    -> );
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> INSERT INTO employee (grp,name) VALUES ("A","A1"),
    ->                                        ("B","B1"),
    ->                                        ("C","C1"),
    ->                                        ("A","A2"),
    ->                                        ("B","B2"),
    ->                                        ("C","C2");
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0
mysql>
mysql> SELECT * FROM employee ORDER BY grp,id;
+-----+----+------+
| grp | id | name |
+-----+----+------+
| A   |  1 | A1   |
| A   |  2 | A2   |
| B   |  1 | B1   |
| B   |  2 | B2   |
| C   |  1 | C1   |
| C   |  2 | C2   |
+-----+----+------+
6 rows in set (0.00 sec)
mysql>
mysql>
mysql> drop table employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>

You can retrieve the most recent AUTO_INCREMENT value with the LAST_INSERT_ID().

LAST_INSERT_ID() is connection-specific.

mysql>
mysql>
mysql> CREATE TABLE employee (
    ->      id MEDIUMINT NOT NULL AUTO_INCREMENT,
    ->      name CHAR(30) NOT NULL,
    ->      PRIMARY KEY (id)
    ->  );
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql> desc employee;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | mediumint(9) | NO   | PRI | NULL    | auto_increment |
| name  | char(30)     | NO   |     |         |                |
+-------+--------------+------+-----+---------+----------------+
2 rows in set (0.01 sec)
mysql>
mysql> INSERT INTO employee (name) VALUES ("A");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> SELECT * FROM employee;
+----+------+
| id | name |
+----+------+
|  1 | A    |
+----+------+
1 row in set (0.00 sec)
mysql>
mysql> select LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                1 |
+------------------+
1 row in set (0.00 sec)
mysql>
mysql> drop table employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>