mysql - 我可以将unit关键字保存到MYSQL中的变量中吗？

Question

我想写一个这样的程序:

CREATE PROCEDURE `addByType`(IN myDate DATETIME, IN myType INT, OUT output DATETIME)
BEGIN
DECLARE unit ?;
CASE  
    WHEN myType = 1 THEN 
        SET unit = HOUR;        
    WHEN myType = 2 THEN
        SET unit = DAY;
    ...
END CASE;
SELECT TIMESTAMPADD(unit, 1, myDate) INTO output;
END

有可能吗？我可以将单位关键字存储到变量中吗？或者还有其他方法可以达到同样的目的吗？

Answer 1

请尝试一下这个:

CREATE PROCEDURE `addByType`(IN myDate DATETIME, IN myType INT, OUT output DATETIME)
BEGIN

CASE  
    WHEN myType = 1 THEN 
        SET @unit = 'HOUR';        
    WHEN myType = 2 THEN
        SET @unit = 'DAY';
END CASE;

SET @sql = CONCAT('SELECT TIMESTAMPADD(', @unit, ', 1, \'', myDate, '\') INTO @output;');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET output = @output;

END

可能包含语法错误，必须查找某些内容。但我相信你能弄清楚。得走了，明天再去看看。

附:Here's the manual entry for prepared statements .