mysql psuedo column in where cluse

Question

目前所有行中的status列爲0，而startdate至少在now()之前幾天，但以下查詢返回空結果集。

 select p.id, (select @days:=(datediff(now(),p.startdate))) as days from poa p 
    where p.status < @days; 

哪裏可能會出錯？

Answer 1

SELECT id , days FROM 
( 
SELECT p.id as id , datediff(now(),p.startdate) as days , p.status as status 
FROM poa p 
) 
t WHERE t.status < t.days;