Question

问题如下：我使用子查询，我需要加入

WITH subselect_from_A AS (
    SELECT A.A_ID FROM A
)
SELECT B.D_ID FROM B, subselect_from_A WHERE B.B_ID = 
A.A_ID
/* or instead: subselect_from_A.A_ID */

如何从子选择中引用该列？

Answer 1

首先，您应该停止使用已弃用的隐式联接并改为使用显式联接。然后你可以使用表别名：

WITH subselect_from_A AS (
    SELECT A.A_ID FROM A --doesn't really seem like a sub-select
)
SELECT B.D_ID, A.A_ID
FROM B
INNER JOIN subselect_from_A AS A
    ON B.B_ID = A.A_ID;

Answer 2

与常规表格相同。

WITH subselect_from_A AS (
    SELECT A.A_ID FROM A
)
SELECT B.D_ID, subselect_from_A.A_ID FROM B, subselect_from_A
WHERE B.B_ID = subselect_from_A.A_ID;

从WITH-Subselect引用列

2 个答案: