Question

I have a mysql table that stores a mapping from an ID to a set of values:

CREATE TABLE `mapping` (
  `ID` bigint(20) unsigned NOT NULL,
  `Value` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

This table is a list of values and the ID of a row selects the set, this value belongs to.
So the column ID is unique per set, but not unique per row.

I insert data into the table using the following statement:

INSERT INTO `mapping`
SELECT 5, `value` FROM `set1`;

In this example I calculated and set the ID manually to 5.
It would be great if mysql could set this ID automatically. I know the autokey feature, but using it will not work, because all rows inserted with the same insert statement should have the same ID.

So each insert statement should generate a new ID and then use it for all inserted rows.
Is there a way to accomplish this?

Answer 1

I am not convinced to it (I’m not sure whether locking table is good idea, I think it’s not), but this might help:

lock tables `mapping` as m write, m as m1 read;

insert into m
select (select max(id) + 1 from m1), `value` from `set1`;

ulock tables;