MySQL子查詢選擇特定列

Question

我有一個返回3列的子查詢。我無法擺脫它們。我只想爲父查詢使用其中一列。

例如。

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

我只想從table_b得到id。

我要找的線沿線的東西：

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

如何我會做到這一點？

Answer 1

如何生根粉這一點：

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; 

是這樣的結果符合你的想法？

Answer 4

我認爲實現這一目標的最好辦法是：

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)