Mysql子查询不显示行

Question

这是我的查询:

SELECT a.vardas, a.pavarde FROM `y6fdt_igym_abonementai` AS a 
INNER JOIN 
( 
    SELECT max(galiojaiki) gal, id, abonementas FROm y6fdt_igym_sutartys
) c
on c.abonementas = a.id

为什么我只看到 a.vardas 和 a.pavarde 列作为结果。但不是 id，abonementas 来自子查询？

Answer 1

如果您想查看这些列，您必须将它们添加到主 SELECT 子句中。

SELECT a.vardas, a.pavarde, c.gal, c.id, c.abonementas
FROM `y6fdt_igym_abonementai` AS a 
INNER JOIN 
( 
    SELECT max(galiojaiki) gal, id, abonementas FROm y6fdt_igym_sutartys
) c
on c.abonementas = a.id

请注意，子查询中的 id 和 abonementas 列不会来自具有 max(galiojaiki) 的行。它只会从表中的某个随机行中取出它们。如果你想要那些特定的值，你需要使用:

SELECT a.vardas, a.pavarde, c.gal, c.id, c.abonementas
FROM `y6fdt_igym_abonementai` AS a 
FROM y6fdt_igym_sutartys AS c ON c.abonementas = a.id
INNER JOIN 
( 
    SELECT max(galiojaiki) AS maxgal 
    FROm y6fdt_igym_sutartys
) d on c.galiojaiki = d.maxgal