使用SQL Server中具有多行的另一个表更新主表行

Question

我有2个具有共同列ID的表

Table A:
ID   value1    value2    value3
------------------------------------        
 1     0         0        0

Table B:
ID    value_type      value   
--------------------------------------          
1     value1          0.01  
2     value2          0.02
3     value3          0.03

我想使用表b的值更新表A的值，

Final Output :

ID   value1    value2    value3
-----------------------------------------
1     0.01       0.02      0.03

谁能告诉我如何编写查询并如上所述获取结果，谢谢！ 我尝试加入，枢纽。 一切都没有结果。

Answer 1

一种快速（但不具有可伸缩性）的解决方案是将update语句与带有条件农业的派生表的联接一起使用：

UPDATE T
SET value1 = v1,
    value2 = v2,
    value3 = v3
FROM TableA T
JOIN 
(
    SELECT 1 As ID
           MAX(CASE WHEN value_type = 'value1' THEN value END) As v1,
           MAX(CASE WHEN value_type = 'value2' THEN value END) As v2,
           MAX(CASE WHEN value_type = 'value3' THEN value END) As v3
    FROM TableB
) V
    ON T.ID = V.ID

Answer 2

使用枢轴，我们可以做到这一点

由于iam将数据存储到一个表中，此后只有iam doinn更新

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX);

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.value_type)
            FROM #b c
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT rn as id , '  + (@cols) + ' into dynamictable  from 
            (
                select *,ROW_NUMBER() OVER(PARTITION BY ID ORDER BY ID ) AS RN
                from #b
           ) x
            pivot 
            (
                MAX(VALUEE)
                for VALUE_TYPE in (' + @cols + ')
            ) p 
          '


exec(@query)
UPDATE T
SET T.value1 = V.value1,
    T.value2 = V.value2,
    T.value3 = V.value3
FROM #a T
JOIN 
(SELECT   id ,MAX(VALUE1)VALUE1 , MAX(VALUE2)VALUE2, MAX(VALUE3)VALUE3 
FROM  dynamictable
GROUP BY id
) V
    ON T.ID = V.ID