Question

我有一个返回3列的子查询。我无法摆脱他们。我想只使用其中一列作为父查询。

例如。

SELECT * FROM table_a WHERE id = (SELECT a,id,b FROM table_b LIMIT 1);

我希望只从id获得table_b。

我正在寻找以下内容：

SELECT * FROM table_a WHERE id = (SELECT a,id,b FROM table_b LIMIT 1)[id];

我将如何做到这一点？

Answer 1

这是怎么回事：

SELECT * FROM table_a WHERE id =
(select id from
 (SELECT a,id,b FROM table_b LIMIT 1)a);

Answer 2

SELECT * 
FROM table_a 
WHERE id IN
    (
        SELECT a FROM tableB limit 1
        UNION
        SELECT id FROM tableB limit 1
        UNION
        SELECT b FROM tableB limit 1
    )

Answer 3

SELECT * FROM table_a, (SELECT a,id,b FROM table_b LIMIT 1) temp_b where table_a.id = temp_b.id;

这个结果与你的想法相符吗？

Answer 4

我认为实现这一目标的最佳方式是：

SELECT * 
FROM table_a
inner join 
 (
       SELECT a as id FROM tableB
        UNION
        SELECT id FROM tableB
        UNION
        SELECT b as id FROM tableB
) tempB on (table_a.id=tempB.id)

MySQL子查询选择特定列

4 个答案: