delimiter //

create procedure upd_userinput(in request_time TIMESTAMP,out time TIME, out user_session_id INT)     

begin      

set time = time(request_time);    

case  
when time < '09:15:00' && time > '08:15:00' then      
set user_session_id = 1; 

when time < '10:15:00' && time > '11:15:00' then
set user_session_id = 2;  

else set user_session_id =3;

end case;  
end //

case必须至少匹配一个给定的语句，否则你会得到这个错误。2为了避免这个错误，在它里面包含一个else。

create procedure upd_userinput(in  request_time timestamp, out user_session_id int) 
begin 
update user_input;
case request_time
when time(request_time) < '9:15:00' && time(request_time) > '8:15:00' then
set user_session_id = 1; 
when  time(request_time)< '10:15:00' && time(request_time) > '11:15:00' then
set user_session_id =2; 
else set user_session_id =0; 
end case; 
end

在mysql存储过程中使用case-when语句的最佳方法是：

DELIMITER $
CREATE PROCEDURE my_pro()
BEGIN
UPDATE users 
SET phone = 
(
    CASE 
        WHEN substr(phone, 2,1) = '3' THEN concat('04', substr(phone, 2))
        WHEN substr(phone, 2,1) = '2' THEN concat('05', substr(phone, 2))
    END
);
END $