MySQL子查詢選擇特定列

Question

我有一個返回3列的子查詢。 我不能擺脫他們。 我只想對父查詢使用一列。

例如。

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

我只想從table_b獲取id 。

我正在尋找以下方面的東西：

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

我將如何完成？

Answer 1

怎么這樣：

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;

這個結果符合您的想法嗎？

Answer 4

我認為實現這一目標的最佳方法是：

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)