CREATE FUNCTION getTargetFloor(message VARCHAR(255),appID INT,tID INT) RETURNS INT
BEGIN
 DECLARE floor INT;
 DECLARE id INT;
 SET floor = 0;
 SET id = 0;
    SELECT `id` INTO id FROM `k`.`comment` WHERE `tid`=tID AND `appid`=appID ORDER BY `id` LIMIT floor,1;
 END IF;
 RETURN(id);
END

mysql> use test;
Database changed
mysql> delimiter $$
mysql> drop procedure if exists getId$$
Query OK, 0 rows affected (0.00 sec)

mysql> create procedure getId(in appID int,in tID int,in lim int)
    -> begin
    -> set @sql=concat('select id into @iid from comment  WHERE appid= ',appID,'
 AND tid= ',tID,' ORDER BY id LIMIT ',lim,',1');
    -> PREPARE stmt from @sql;
    -> EXECUTE stmt;
    -> end ;$$
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;
mysql> CALL getID(25,3399,0);
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT @iid;
+--------+
| @iid   |
+--------+
| 144000 |
+--------+
1 row in set (0.00 sec)

mysql>

------解决方案--------------------
SQL code
DELIMITER $$
CREATE FUNCTION getTargetFloor(message VARCHAR(255),appID INT,tID INT) RETURNS INT
BEGIN
 DECLARE `floor` INT;
 DECLARE Aid INT;
 SET `floor` = 0;
 SET Aid = 0;
  SELECT `id` INTO Aid FROM `k`.`comment` WHERE `tid`=tID AND `appid`=appID ORDER BY `id` LIMIT FLOOR,1;
 RETURN Aid;
END$$
DELIMITER ;