3 表 sql 总和除以两个字段之间的负数不起作用

Question

我有 3 个表：formulario、viaverde 和 reparacoes。 其中一个字段在所有表中都是相等的，称为 matricula，我试图将每个算术运算分组到它。 但我一直收到 matricula is ambiguous 或 synthax 错误的错误，我该如何实现？

我尝试了以下代码：

JOIN (
    SELECT matricula, (total)/(kmsTotais) AS custoKM
    FROM (
        SELECT matricula, SUM(kmfim - quilometragem) AS kmsTotais
        FROM formulario
        GROUP BY matricula
    ) e
    JOIN (
        SELECT matricula, abastecimento_euros as total FROM formulario
        UNION ALL
        SELECT matricula, custo as total FROM viaverde
        UNION ALL
        SELECT matricula, valor as total FROM reparacoes
    ) as subquery
    GROUP BY matricula
) i ON i.matricula = f.matricula

Answer 1

您需要使用表别名限定 matricula 以使其明确。

JOIN (
    SELECT e.matricula, SUM(total)/MAX(kmsTotais) AS custoKM
    FROM (
        SELECT matricula, SUM(kmfim - quilometragem) AS kmsTotais
        FROM formulario
        GROUP BY matricula
    ) e
    JOIN (
        SELECT matricula, abastecimento_euros as total FROM formulario
        UNION ALL
        SELECT matricula, custo as total FROM viaverde
        UNION ALL
        SELECT matricula, valor as total FROM reparacoes
    ) as subquery ON e.matricula = subquery.matricula
    GROUP BY e.matricula
) i ON i.matricula = f.matricula

您也可以将 ON e.matricula = subquery.matricula 替换为 USING (matricula)。因为这表明列名在两个表中是相同的，所以您不需要限定该列。