MySQL语法-变量的标准偏差，而不是列

我试图找到用于计算存储过程中一组变量的标准偏差的语法

我希望能做这样的事情：

set variable1 = 5;
set variable2 = 7;
set variable3 = 8;
set variable4 = 2;

set MyStandardDeviation = StdDev(variable1, Variable2, variable3, variabl4)

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您可以使用

UNION ALL

组合并生成一列临时表

set variable1 = 5;
set variable2 = 7;
set variable3 = 8;
set variable4 = 2;

set MyStandardDeviation = 
            (
                SELECT StdDev(x.Val)
                FROM 
                    (
                        SELECT variable1 As Val
                        UNION ALL
                        SELECT variable2 As Val
                        UNION ALL
                        SELECT variable3 As Val
                        UNION ALL
                        SELECT variable4 As Val
                    ) x
            );

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可能复制的优秀！工作起来很有魅力。谢谢！