Question

这就是我想要做的（简化查询）：

SELECT
 FOO.id,
 FOO.maxTickets,
 (SELECT COUNT(*) countx FROM barfoo BAR WHERE BAR.idt = FOO.id) buyTickets,
 (FOO.maxTickets - buyTickets) leftTickets
FROM
 foobar FOO
ORDER BY
 FOO.leftTickets ASC

但是当我这样做时，我有这样的信息：

   #1054 - Unknown column 'buyTickets' in 'field list'

我很困惑。请帮帮我。

谢谢！

Answer 1

您不能使用您在选择列表中指定的别名，因此不知道buyTickets是否在另一个计算中使用。解决这个问题的一种方法是使用子查询：

select id, 
    maxTickets, 
    buyTickets, 
    maxTickets - buyTickets as leftTickets
from
(
     SELECT FOO.id,
        FOO.maxTickets,
        (SELECT COUNT(*) countx 
             FROM barfoo BAR WHERE BAR.idt = FOO.id) buyTickets
    FROM foobar FOO
) d
ORDER BY leftTickets ASC

Answer 2

列buyTickets没有在那里定义（别名而不是表列）。要么重复计数，要么使用内部查询：

SELECT
    id,
    maxTickets,
    (SELECT COUNT(*) countx FROM barfoo BAR WHERE BAR.idt = FOO.id) buyTickets,
    (FOO.maxTickets - (SELECT COUNT(*) countx FROM barfoo BAR WHERE BAR.idt = FOO.id)) leftTickets
FROM
    foobar FOO
ORDER BY
    leftTickets ASC

Mysql子查询计算（错误1054）

2 个答案: