Question

我创建了一个程序，从各种项目（数据库）中动态收集一些记录到临时表中，并从我插入表中的临时表中。使用WHERE语句，但不幸的是，当我检查执行计划时，我发现，这个查询部分需要大量的负载。如何优化此INSERT部分或WHERE声明？

INSERT INTO dbo.PROJECTS_TESTS ( PROJECTID, ANOTHERTID, DOMAINID, is_test)
    SELECT * FROM #temp_Test AS tC
    WHERE NOT EXISTS (SELECT TOP 1 1 
                        FROM dbo.PROJECTS_TESTS AS ps WITH (NOLOCK)
                        WHERE ps.PROJECTID = tC.projectId 
                        AND ps.ANOTHERTID = tC.anotherLink 
                        AND ps.DOMAINID = tC.DOMAINID 
                        AND ps.is_test = tC.test_project 
                        )

Answer 1

我认为通过JOIN而不是EXISTS可以提供更好的服务。根据加入条件的基数（当前位于WHERE中），您可能还需要DISTINCT。

INSERT INTO dbo.PROJECTS_TESTS ( PROJECTID, ANOTHERTID, DOMAINID, is_test)
    SELECT <maybe distinct> tC.* FROM #temp_Test AS tC
    LEFT OUTER JOIN  FROM dbo.PROJECTS_TESTS AS ps on
                        ps.PROJECTID = tC.projectId 
                        AND ps.ANOTHERTID = tC.anotherLink 
                        AND ps.DOMAINID = tC.DOMAINID 
                        AND ps.is_test = tC.test_project 

where ps.PROJECT ID IS NULL

或类似的东西

SQL如何从临时表优化插入到表

1 个答案: