Question

这是该问题的后续内容。

How do I UPDATE from a SELECT in SQL Server?

如果我使用问题2334712的查询，如何在Table_A中插入“ ABC”，“ BCD”或“ DEF”？

我尝试过，但是不能在查询中使用ORDER BY子句。

查询结果应该是ABC（如果是升序）或DEF（如果是降序），或者基于另一列上的键，则说B3。

UPDATE
    Table_A
SET
    Table_A.A2 = Table_B.B2
FROM
    Table_A
    INNER JOIN Table_B
        ON Table_A.A1 = Table_B.B1
WHERE
    Table_A.A1 < 10

Table_A:
        A1 A2
        1       (desired result: can insert 'ABC' or 'DEF' based on my choice)
        2 



Table_B:
        B1 B2  B3
        1  ABC 1
        1  BCD 2
        1  DEF 3
        2  GHI 4

Answer 1

加入一个子查询，该子查询为B1的每个值标识一条记录：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY B1 ORDER BY B2) rn
    FROM Table_B
)

UPDATE a
SET A2 = b.B2
FROM Table_A a
INNER JOIN cte b
    ON a.A1 = b.B1 AND b.rn = 1
WHERE
    a.A1 < 10;

此示例假设您希望记录的每个B2值都具有最低的B1值。但是，您可以将呼叫更改为ROW_NUMBER，但是要使用其他顺序。

Answer 2

您可以在下面使用row_number（）尝试

WITH t1 AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY B1 ORDER BY B3 desc) rownum
    FROM Table_B
)

UPDATE a
SET A2 = b.B2
FROM Table_A a
INNER JOIN t1 b
    ON a.A1 = b.B1 AND rn=1
WHERE
    a.A1 < 10;

或者您可以使用相关子查询

UPDATE a
    SET A2 = b.B2
    FROM Table_A a
    INNER JOIN Table_B b
        ON a.A1 = b.B1 AND exists (select max(B3) from Table_B c on b.B1 and c.B1)
    WHERE
        a.A1 < 10;

Answer 3

您可以使用“ with”表，像这样：

    WITH AAA (T_B, ID)
AS
(
SELECT  TOP (SELECT COUNT(*) FROM Table_A)  Table_B.B2 AS RR ,Table_A.A1
FROM Table_A INNER JOIN Table_B
  ON Table_A.A1 = Table_B.B1
WHERE Table_A.A1 < 10
ORDER BY 1 DESC-- OR ASC

)
UPDATE Table_A
SET Table_A.A2 = T_B
FROM AAA

如何从SQL Server中的SELECT更新-如果选择返回多个项目（跟进问题2334712）

3 个答案: