Question

我需要在sql server 2008中合并两个表，通过productid字段过滤源和目标，假设我有一个源表@source（productid，userid）和@target具有相同的结构，我需要合并两个表，但仅适用于具有指定productid的记录。

上面的示例确定我只需要知道是否有更好的方法只删除productId = @ productId与源不匹配的记录与添加“和TARGET.productid = @productid”运算符相比较不符合来源？

感谢。

declare @productid int = 1
declare @source table (productid int, userid int)
declare @target table (productid int, userid int)
insert into @source (productid , userid ) values(1,1)
insert into @source (productid , userid ) values(1,2)
insert into @source (productid , userid ) values(1,3)
insert into @source (productid , userid ) values(2,1)
insert into @source (productid , userid ) values(2,2)
insert into @source (productid , userid ) values(2,3)

insert into @target (productid , userid ) values(1,4)
insert into @target (productid , userid ) values(2,5)
insert into @target (productid , userid ) values(3,1)
insert into @target (productid , userid ) values(4,1);

WITH n (productid , userid )
AS
(
select productid , userid from @source where productid = @productid
)
MERGE @target AS TARGET 
USING n  AS SOURCE 
ON (TARGET.productid = SOURCE.productid and TARGET.userid = SOURCE.userid) 
WHEN NOT MATCHED BY TARGET THEN 
INSERT (productid , userid) 
VALUES (SOURCE.productid, SOURCE.userid)
WHEN NOT MATCHED BY SOURCE and TARGET.productid  = @productid  THEN 
DELETE;

select * from @target order by 1,2

Answer 1

目标表不必是SQL Server中的基表。它可以是CTE，派生表，甚至是视图。

旧：

MERGE @target AS TARGET

新：

MERGE (SELECT * FROM @target WHERE ArbitraryCondition) AS TARGET

使用ArbitraryCondition按您喜欢的方式按productid进行过滤。

Answer 2

你应该避免使用 MERGE语句。你应该避免阅读Aaron Bertrand的这篇文章 Use Caution with SQL Server's MERGE Statement 。< / p>

您可以使用简单连接或EXISTS执行此操作。见下文..

插入声明

INSERT INTO Target (productid , userid)
SELECT S.productid , S.userid
FROM Source s LEFT JOIN Target T
ON T.productid = S.productid AND T.userid = S.userid
WHERE S.userid IS NULL OR S.productid IS NULL
AND  productid =  -- Specify your targeted Ids

删除语句

DELETE FROM S
FROM Source S LEFT JOIN Target T
ON T.productid = S.productid AND T.userid = S.userid
WHERE S.userid IS NULL OR S.productid IS NULL

什么是使用merge语句过滤目标表的最佳方法

2 个答案: