Question

In mysql it is possible to make a fork in the command “SET”?

Like this:

UPDATE `table`.`data` SET `hits` = (`hits`-1<0 ? 0:`hits`-1) WHERE `data`.`id`='15';

Answer 1

Use the IF function:

UPDATE `table`.`data`
SET `hits` = IF(`id` - 1 > 0, 0, `id` - 1)
WHERE `data`.`id`='15';

In this specific case you could also use LEAST.

UPDATE `table`.`data`
SET `hits` = LEAST(`id` - 1, 0)
WHERE `data`.`id`='15';

Your code seems wrong though. I’m almost certain that you meant to write this:

UPDATE yourtable
SET hits = GREATEST(0, hits - 1)
WHERE id = 15;