mysql - 我可以使用具有某些函数值的变量吗

Question

是否有像这样使用变量的合法方式:

SELECT dr.id, @diff:=DATEDIFF(NOW(), DATE_ADD(dr.dt, INTERVAL dr.payment_session DAY))
FROM `dst_request` as dr
WHERE @diff >= 0 OR @diff <=5

它不会抛出那样的错误，但也不会返回正确的结果。它是有效的查询吗？谢谢!

Answer 1

使用派生表:

SELECT 
    id, 
    diff
FROM (
        SELECT
            dr.id,
            DATEDIFF(NOW(), DATE_ADD(dr.dt, INTERVAL dr.payment_session DAY)) as diff
         FROM `dst_request` as dr
) as t
WHERE diff >= 0 OR diff <=5

如果有语法或格式错误，请原谅我，因为我是在浴缸里用手机转录的。这个概念是正确的。