mysql中的递减值但不是负数 [英] Decrement value in mysql but not negative

问题描述

当用户在php和mysql中删除它时，我想减小一个值.我要检查是否小于0.如果值为0，则不要减量.

I want to decrement a value when user delete it in php and mysql. I want to check not to go below than 0. If value is 0 then do not decrement.

mysql_query("UPDATE table SET field = field - 1 WHERE id = $number");

如果字段为 0 ，则不执行任何操作

If field is 0 then do not do anything

推荐答案

添加另一个条件，仅在field大于0

Add another condition to update only if the field is greater 0

UPDATE table 
SET field = field - 1
WHERE id = $number
and field > 0

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