Mysql子查询计算(错误1054)

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

但是当我这样做的时候，我得到了这个消息:

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

我很困惑。请帮助我。

谢谢!

Answer 1

buyTickets 列没有在那里定义(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