MySQL子查询出错

Question

我有一个MySQL查询来生成一个显示两列的视图，这两列是子查询但由于某种原因我收到错误。

SELECT 
(SUM(cards_required) FROM `orders` WHERE statuses = 1) As Count,
(SUM(cards_required) FROM `orders` WHERE statuses = 2) As Count
FROM `orders` WHERE user_id = 1

错误消息

  

＃1064 - 您的SQL语法出错;检查与MySQL服务器版本对应的手册，以获得正确的语法   'FROM orders WHERE statuses = 1附近）作为Count，（SUM（cards_required）   来自第3行的订单

Answer 1

您使用的语法不太正确。您可以使用IF有条件地求和：

SELECT 
SUM(IF(statuses = 1,cards_required,0)) As status_1,
SUM(IF(statuses = 2,cards_required,0)) As status_2
FROM `orders` WHERE user_id = 1