mysql - SQL命令错误

Question

我是 SQL 新手，有人可以回答我有什么问题吗？!谢谢。

SELECT  
     bom.Parent_Material_Number, 
     mm.Material_Number, 
     mm.Material_Descr_HU,
     bom.Child_Material_Number
FROM mm,bom
GROUP BY mm.Material_Descr_HU

Answer 1

您的查询有误。如果您打算使用 GROUP BY 子句，请确保取消分组字段具有聚合，例如 SUM()、MIN()、MAX() 等。请参阅下面的示例:

SELECT  
      MIN(bom.Parent_Material_Number), 
      MAX(mm.Material_Number), 
      mm.Material_Descr_HU,
      MIN(bom.Child_Material_Number)
FROM  mm,bom
WHERE bom.Parent_Material_Number = mm.Material_Number
GROUP BY mm.Material_Descr_HU;

您还可以显式联接。见下文:

    SELECT  
          MIN(bom.Parent_Material_Number), 
          MAX(mm.Material_Number), 
          mm.Material_Descr_HU,
          MIN(bom.Child_Material_Number)
    FROM mm INNER JOIN bom
    ON bom.Parent_Material_Number = mm.Material_Number
    GROUP BY mm.Material_Descr_HU;