mysql - MySQL子查询选择特定列

Question

我有一个返回 3 列的子查询。我无法摆脱它们。我只想将其中一列用于父查询。

例如。

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

我只想id从table_b.

我正在寻找类似的东西：

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

怎么样：

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;

这个结果符合你的想法吗？

Answer 4

我认为实现这一目标的最佳方法是：

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)