mysql - 表列作为变量

Question

当我尝试使用变量作为对表列的引用时，我的存储过程中出现语法错误。

BEGIN
SET @mycolumn = (SOME SELECT STATEMENT RETURNING MY COLUMN);
SELECT a.@mycolumn FROM mytable as a;
END

问题:我的语法有什么问题？

Answer 1

看起来您正在尝试执行动态 SQL。这是一种方法:

BEGIN
SET @mycolumn = (SOME SELECT STATEMENT RETURNING MY COLUMN);
DECLARE @sql varchar(20000); 
SET @sql = CONCAT('SELECT a.', @mycolumn, ' FROM mytable as a';
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END