MySQL auto-increment based on group

Question

The problem is related to autoincrement with mysql. What I\'m trying to achieve is to increment an ID value based on the customer number. So basically i insert data sets without

Answer 1

you can use a query like this:

INSERT INTO autoinc (cid,info,customer)
SELECT
    COALESCE(max(cid),0) +1
    , 'A Customer 1'
    , 12345
FROM autoinc
WHERE customer = 12345;

sample

mysql> SELECT * from autoinc;
Empty set (0,00 sec)

mysql> INSERT INTO autoinc (cid,info,customer)
    -> SELECT
    ->     COALESCE(max(cid),0) +1
    ->     , 'A Customer 1'
    ->     , 12345
    -> FROM autoinc
    -> WHERE customer = 12345;
Query OK, 1 row affected (0,00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> SELECT * from autoinc;
+----+------+--------------+----------+
| id | cid  | info         | customer |
+----+------+--------------+----------+
|  1 |    1 | A Customer 1 |    12345 |
+----+------+--------------+----------+
1 row in set (0,00 sec)

mysql> INSERT INTO autoinc (cid,info,customer)
    -> SELECT
    ->     COALESCE(max(cid),0) +1
    ->     , 'A Customer 1'
    ->     , 12345
    -> FROM autoinc
    -> WHERE customer = 12345;
Query OK, 1 row affected (0,00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> SELECT * from autoinc;
+----+------+--------------+----------+
| id | cid  | info         | customer |
+----+------+--------------+----------+
|  1 |    1 | A Customer 1 |    12345 |
|  2 |    2 | A Customer 1 |    12345 |
+----+------+--------------+----------+
2 rows in set (0,00 sec)

mysql> INSERT INTO autoinc (cid,info,customer)
    -> SELECT
    ->     COALESCE(max(cid),0) +1
    ->     , 'B Customer 2'
    ->     , 9876
    -> FROM autoinc
    -> WHERE customer = 9876;
Query OK, 1 row affected (0,00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> SELECT * from autoinc;
+----+------+--------------+----------+
| id | cid  | info         | customer |
+----+------+--------------+----------+
|  1 |    1 | A Customer 1 |    12345 |
|  2 |    2 | A Customer 1 |    12345 |
|  3 |    1 | B Customer 2 |     9876 |
+----+------+--------------+----------+
3 rows in set (0,00 sec)

mysql> INSERT INTO autoinc (cid,info,customer)
    -> SELECT
    ->     COALESCE(max(cid),0) +1
    ->     , 'A Customer 1'
    ->     , 12345
    -> FROM autoinc
    -> WHERE customer = 12345;
Query OK, 1 row affected (0,00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> SELECT * from autoinc;
+----+------+--------------+----------+
| id | cid  | info         | customer |
+----+------+--------------+----------+
|  1 |    1 | A Customer 1 |    12345 |
|  2 |    2 | A Customer 1 |    12345 |
|  3 |    1 | B Customer 2 |     9876 |
|  4 |    3 | A Customer 1 |    12345 |
+----+------+--------------+----------+
4 rows in set (0,00 sec)

mysql>