Mysql的子查询没有显示行

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，subquery的abonementas？

Answer 1

如果您想查看这些列，则必须将它们添加到主要的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 

注意，在子查询的id和abonementas列将无法从一行max(galiojaiki)。它会从表格中随机选取一行。如果你想那些特定的值，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 

Answer 2

变化

SELECT a.vardas, a.pavarde FROM `y6fdt_igym_abonementai` AS a 
... 
SELECT max(galiojaiki) gal, id, abonementas FROm y6fdt_igym_sutartys 

到

SELECT a.vardas, a.pavarde FROM `y6fdt_igym_abonementai` a 
... 

SELECT max(c.galiojaiki) c.gal, c.id, c.abonementas FROm y6fdt_igym_sutartys c