mysql - MySQL 语法 - 变量的标准偏差，而不是列

Question

我试图找到语法来计算存储过程中一组变量的标准偏差。

我希望能够做这样的事情：

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

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

Answer 1

您可以使用UNION ALL组合和生成一列临时表，

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
            );