mysql - MySQL语法-变量而非列的标准差

我试图找到语法来计算存储过程中一组变量的标准差。
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)

最佳答案

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
            );