我有类似于此的查询,此代码可以工作,但存在性能问题:LEFT JOINMaterialsID, SUM(Quantity) AS Quantity FROM Incoming GROUP BY MaterialsID ) AS Inc
ON Inc.MaterialsID=Mat.IDLEFT JOIN ( SELECT MaterialsID, SUM(Quantity) AS Quantity FROM
SQL表由列calling_party、called_party和call_duration组成。示例记录如下:A,C,12B,R,56对于存储在calling_party和called_party两个角色中的每个用户,我想要进行统计,例如,传入会话的总持续时间,传出会话的数量等。SELECT DISTINCT FROM INNER JOIN