Question

I have a table (foo) where I already have a PK on id:

id      name      rank
-----------------------
 1      AAAA        2
 2      BBBB        1

I want to insert a new row where I know the values of column id and name and want rank to take a value greater than any other value in the same column in preceding rows (similar to what auto_increment does for us).

i.e. if I were to add a row with value = CCCC, the rank column should have a value 3. I need to do this in a compound statement if possible. I tried the following which does not work.

insert into foo (`name`, `rank`)
values ('CCCC', (select max(`rank`) from `foo`))

Which gives me the following error:

You can't specify target table 'foo' for update in FROM clause

Note: I would ideally like to have the rank column as an auto_increment field, but apparently that’s not allowed either, since I already have a PK.

PS: I need to be able to execute this statement from PHP without using stored procedures.

Answer 1

Try this first, it being derived instantly from your post:

INSERT INTO foo (`name`, `rank`)
SELECT 'CCCC', (MAX(`rank`) + 1) AS rank
FROM `foo`

Then using PDO, I think this’ll work:

...
$sql = "INSERT INTO foo (`name`, `rank`) SELECT ?, (MAX(`rank`) + 1) AS rank FROM `foo`"
$name = "CCCC";
$st = $pd->prepare($sql);
$st->bindValue(1, $name);

try {
    $retval = $st->execute();
} catch (PDOException $pdoex) {
...

Not sure if I got in syntactically correct but that should be about the gist of it … I think

Err.. lemme know if the SQL works, at least 😀