MySQL子查詢不顯示行

Question

這是我的查詢：

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

為什么我只能看到a.vardas和a.pavarde列。 但不是id，來自子查詢的abonementas嗎？

Answer 1

如果要查看這些列，則必須將它們添加到主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

請注意，子查詢中的id和abonementas列將不會來自具有max(galiojaiki) 。 它只會從表中的某些隨機行中提取它們。 如果需要這些特定值，則需要使用：

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

更改

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

至

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