MySQL 不识别虚拟列/字段答案

【问题标题】：MySQL not recognizing virtual column / fieldMySQL 不识别虚拟列/字段
【发布时间】：2012-12-10 12:07:02
【问题描述】：

我正在尝试将子查询生成的两个虚拟字段操作到一个新字段中，但 MySQL 告诉我“GP”是一个未知列，但它已经被声明了。请看一下我的查询：

SELECT *,

(SELECT COUNT(id_gol) FROM tb_gol as gol
INNER JOIN tb_jogo as jg ON(gol.fk_id_jogo = jg.id_jogo)
WHERE gol.ic_excluido != '*' AND gol.fk_id_equipe = e.id_equipe AND jg.fk_id_campeonato = g.fk_id_campeonato) as 'GP',

(SELECT COUNT(id_gol) FROM tb_gol as gol
INNER JOIN tb_jogo as jg ON(gol.fk_id_jogo = jg.id_jogo)
WHERE gol.ic_excluido != '*' AND gol.fk_id_equipe != e.id_equipe AND (jg.fk_id_equipe1 = e.id_equipe OR jg.fk_id_equipe2 = e.id_equipe) AND jg.fk_id_campeonato = g.fk_id_campeonato) as 'GC',

(SELECT COUNT(id_wo) as WOs FROM tb_wo as w INNER JOIN tb_jogo as j ON (w.fk_id_jogo = j.id_jogo) WHERE w.fk_id_equipe = e.id_equipe AND j.fk_id_campeonato = g.fk_id_campeonato) as 'WO',

(GP+(GC*-1)) as 'SALDO'

FROM tb_equipe as e
INNER JOIN tb_gruposEquipes as ge ON (e.id_equipe = ge.fk_id_equipe)
INNER JOIN tb_grupos as g ON (g.id_grupo = ge.fk_id_grupo)
WHERE g.fk_id_campeonato = 23
ORDER BY WO ASC

如您所见，“SALDO”将是“GP-GC”的结果。但是 MySQL 不识别这些列

我该如何解决这个问题？

解决方案

非常感谢你们的帮助，伙计们，但我找到了问题所在。 “SALDO”不能通过减去GP的GC来创建，因为“GP”和“GC”在运行时不存在。

因此，当您需要在运行时操作虚拟字段时，您将不得不重复生成虚拟字段的代码。

那么，如果你有这个选择：

SELECT *, (field1+1) as 'GP', (field2+1) as 'GC', (GP+GC) as 'SALDO' FROM (...)

你需要用这个替换它：

SELECT *, (field1+1) as 'GP', (field2+1) as 'GC', ((field1+1)+(field2+1)) as 'SALDO' FROM (...)

【问题讨论】：

可以在查询选择列表中使用别名来为列指定不同的名称。您可以在GROUP BY、ORDER BY 或HAVING 子句中使用别名来引用该列。查看手册 dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html 。您是在某种脚本中使用此查询还是只是 sql？
能否添加tb_equipe、tb_gruposEquipes和tb_grupos的表结构。这是一个漂亮的小网络应用程序，可帮助进行组调试：sqlfiddle.com

标签： mysql subquery virtual field

【解决方案1】：

将内容推入内部查询

    SELECT core.*,
    (GP+(GC*-1)) as 'SALDO'

    from (

    (SELECT COUNT(id_gol) FROM tb_gol as gol
    INNER JOIN tb_jogo as jg ON(gol.fk_id_jogo = jg.id_jogo)
    WHERE gol.ic_excluido != '*' AND gol.fk_id_equipe = e.id_equipe AND jg.fk_id_campeonato = g.fk_id_campeonato) as 'GP',

    (SELECT COUNT(id_gol) FROM tb_gol as gol
    INNER JOIN tb_jogo as jg ON(gol.fk_id_jogo = jg.id_jogo)
    WHERE gol.ic_excluido != '*' AND gol.fk_id_equipe != e.id_equipe AND (jg.fk_id_equipe1 = e.id_equipe OR jg.fk_id_equipe2 = e.id_equipe) AND jg.fk_id_campeonato = g.fk_id_campeonato) as 'GC',

    (SELECT COUNT(id_wo) as WOs FROM tb_wo as w INNER JOIN tb_jogo as j ON (w.fk_id_jogo = j.id_jogo) WHERE w.fk_id_equipe = e.id_equipe AND j.fk_id_campeonato = g.fk_id_campeonato) as 'WO' ) 


    FROM tb_equipe as e

    ) as core 
    INNER JOIN tb_gruposEquipes as ge ON (core.id_equipe = ge.fk_id_equipe)
    INNER JOIN tb_grupos as g ON (g.id_grupo = ge.fk_id_grupo)
    WHERE g.fk_id_campeonato = 23
    ORDER BY WO ASC

【讨论】：