MariaDB將聚合函數名稱作為存儲過程參數傳遞

Question

我正在寫存儲過程，該過程將聚合函數名和列名作為參數並返回值（例如：（'sum'，'age'）返回值（從myTable中選擇SELECT SUM（age）））

我的代碼：

CREATE PROCEDURE sample (IN name VARCHAR(10), IN col VARCHAR(30), OUT result INT) 
BEGIN
    SELECT CONCAT( name , '(', col, ') ') INTO result FROM myTable;
END$

Answer 1

將其設置為FUNCTION

return CONCAT('SELECT ', name, '(', col, ') FROM myTable;');

Answer 2

使用准備好的語句 。

CREATE PROCEDURE sample (IN name VARCHAR(10), IN col VARCHAR(30), OUT result INT) 
BEGIN
    SET @sql := '';
    SET @ret := 0;

    SELECT CONCAT('SELECT ', name,  '(', col, ') INTO @ret FROM myTable') INTO @sql FROM DUAL;
    PREPARE STMT from @sql;
    EXECUTE STMT;

    SELECT @ret INTO result FROM DUAL;

    DEALLOCATE PREPARE STMT;     
END