如何在兩個select之間使用算術減號mysql？

Question

select player.ActionTime from question_log log inner join player_question player 
where log.ActionType='96' 

select player.ActionTime from question_log log inner join player_question player 
where log.ActionType='97' 

如何使這種情況發生在mysql語法中？選擇ActionType爲96的Actiontime減去另一個爲97.算術minus。

Answer 1

SELECT t96.ActionTime - t97.ActionTime 
FROM 
(
    select player.ActionTime 
    from question_log log 
    inner join player_question player 
    where log.ActionType='96' 
) t96 
CROSS JOIN 
(
    select player.ActionTime 
    from question_log log 
    inner join player_question player 
    where log.ActionType='97' 
) t97 

注意，似乎沒有成爲任何你的兩個查詢之間的關係，所以我只能提出一個CROSS JOIN（笛卡爾乘積）。如果你有多行log.ActionType ='96'或者log.ActionType ='97'，你將會有很多結果行。

Answer 2

使用子查詢：

SELECT player.ActionTime - (SELECT player.ActionTime from question_log log inner join  player_question player where log.ActionType='97' LIMIT 1) 
from question_log log inner join player_question player where log.ActionType='96'