Assign In SELECT Command for MySQL Not working - mysql

Question

I am trying to assign the #lastupd variable. as in below line:
select #lastupd := max(`last_edited_time`)
from flyspray_comments where task_id = taskID;
But mysql give me error:
ERROR 1064 (42000): You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the right
syntax to use near 'BEGIN
set #lastupd = 0; select #lastupd := max(last_edited_time) from
flys' at line 2
The code:
delimiter $$
use flyspray $$
CREATE function last_upd_time(taskID INT)
BEGIN
set #lastupd = 0;
select #lastupd := max(`last_edited_time`) from flyspray_comments where task_id = taskID;
RETURN #lastupd;
END
$$
delimiter ;

Answer 1

Your immediate error has nothing to do with assignment. It is caused by the invalid definition of the function. You're missing mandatory RETURNS clause which indicates the return type of the function. See CREATE FUNCTION Syntax.
There is no need to use a variable in your case, less a user(session) variable. Just RETURN the result of the query.
And since you may use the only statement there is no need in a BEGIN ... END block and changing DELIMITER
That being said a streamlined and working version of your function may look like
CREATE FUNCTION last_upd_time(_task_id INT)
RETURNS DATETIME -- mandatory clause
RETURN -- just return the result of the query
(
SELECT MAX(last_edited_time)
FROM flyspray_comments
WHERE task_id = _task_id
); -- use default delimiter since it's a one-statement function
Here is SQLFiddle demo
Now, if you'd like to use a variable for some reason then
use a local instead of user(session) one.
assign a value with either SET or SELECT ... INTO syntax.
It may look like
DECLARE lastupd DATETIME DEFAULT NULL; -- or 0
SET lastupd =
(
SELECT MAX(last_edited_time)
FROM flyspray_comments
WHERE task_id = _task_id
);
or
DECLARE lastupd DATETIME DEFAULT NULL; -- 0
SELECT MAX(last_edited_time)
INTO lastupd
FROM flyspray_comments
WHERE task_id = _task_id;