Mysql根据逻辑在存储过程中动态构建查询字符串

Question

目标是根据输入变量在Mysql存储过程中更改查询字符串。

像这样：

CREATE DEFINER=`root`@`localhost` PROCEDURE `func`(type VARCHAR(15)) 
BEGIN 
    SET @type = type; 

    -- Check for the sort parameter 
    if @type="asc" THEN 
     SET @sort = " order by name asc"; 
    elseif @type="desc" THEN 
     SET @sort = " order by name desc"; 
    else 
     SET @sort =""; 
    end if; 

SELECT id, name from table @sort; 

END  

Answer 1

的解决方案是使用执行和CONCAT：

CREATE DEFINER=`root`@`localhost` PROCEDURE `test`(input VARCHAR(15)) 
BEGIN 
SET @input = input; 

if @input="asc" then 
    SET @sort = " order by ActivityLogKey asc"; 
elseif @input = "desc" then 
    SET @sort = " order by ActivityLogKey desc"; 
else 
    SET @sort =""; 
end if; 

SET @query = CONCAT('select * from activitylog ',@sort,' limit 0, 5'); 

PREPARE stmt FROM @query; 
EXECUTE stmt; 
DEALLOCATE PREPARE stmt; 

END