mysql - 为什么我的sql用了Max函数却不能用Abs函数？

Question

我有一个表 [tblFull1 04WoodsideTransportV335]，所有数据都来自该表。我想获得压力为最大值、最小值或绝对值的 [数据位置] 和 [load_case]。它适用于 Max 和 Min。 但由于某些原因，它不适用于 Abs。它在 ms Access 2013 中运行。我使用 vba 以编程方式生成查询。

Abs 和 max, min 运算符之间有什么区别导致它不起作用吗？

当 Abs 查询运行时，出于某种原因它会广告“As Expr1”，为什么要这样做？

我知道 SQL 看起来很糟糕，但它确实有效。如果您对如何改进它有任何建议，请告诉我。

抱歉我的英语不好，我是挪威人。

带有 MAX 函数的 SQL:

SELECT DISTINCT 
    t1.[load_case], t2.[Data Location] AS Nodenr, 
    t2.[MaxOfHoop Stress N/mm^2]
FROM 
    [tblFull1 04WoodsideTransportV335] AS t1,
    (SELECT 
         [tblFull1 04WoodsideTransportV335].[Data Location],
         MAX([tblFull1 04WoodsideTransportV335].[Hoop Stress N/mm^2]) AS [MaxOfHoop Stress N/mm^2]
     FROM 
         [tblFull1 04WoodsideTransportV335]
     GROUP BY 
         [tblFull1 04WoodsideTransportV335].[Data Location]
     HAVING ((([tblFull1 04WoodsideTransportV335].[Data Location])
        In (SELECT [Data Location]
            FROM [tblFull1 04WoodsideTransportV335]
            GROUP BY [Data Location]
            HAVING Count(*) > 1)) 
       AND ((MAX([tblFull1 04WoodsideTransportV335].[Hoop Stress N/mm^2])) Is Not Null))
     ORDER BY 
         [tblFull1 04WoodsideTransportV335].[Data Location]) AS t2
WHERE 
    ((t1.[Hoop Stress N/mm^2]) = [t2].[MaxOfHoop Stress N/mm^2])
ORDER BY 
    t1.[load_case] DESC;

带 Abs 函数的 SQL:

SELECT DISTINCT 
    t1.load_case, t2.[Data Location] AS Nodenr, 
    t2.[AbsOfHoop Stress N/mm^2] AS Expr1
FROM 
    [tblFull1 04WoodsideTransportV335] AS t1,
    (SELECT 
         [tblFull1 04WoodsideTransportV335].[Data Location],
         ABS([tblFull1 04WoodsideTransportV335].[Hoop Stress N/mm^2]) AS[AbsOfHoop Stress N/mm^2]
     FROM [tblFull1 04WoodsideTransportV335]
     GROUP BY [tblFull1 04WoodsideTransportV335].[Data Location]
     HAVING ((([tblFull1 04WoodsideTransportV335].[Data Location])
                In (SELECT [Data Location]
                    FROM [tblFull1 04WoodsideTransportV335] 
                    GROUP BY [Data Location]
                    HAVING Count(*) > 1)) 
        AND ((ABS([tblFull1 04WoodsideTransportV335].[Hoop Stress N/mm^2])) Is Not Null))
     ORDER BY 
         [tblFull1 04WoodsideTransportV335].[Data Location]) AS t2
WHERE 
    (((t1.[Hoop Stress N/mm^2])=[t2].[AbsOfHoop Stress N/mm^2]))
ORDER BY 
    t1.load_case DESC;

Answer 1

在 SQL 中，在“HAVING”语句中，只能使用“GROUP BY”中定义的列。对于其他列，您必须在聚合函数中使用 then，它们是: - AVG() - 返回平均值 - COUNT() - 返回行数 - FIRST() - 返回第一个值 - LAST() - 返回最后一个值 - MAX() - 返回最大值 - MIN() - 返回最小值 - SUM() - 返回总和