sql trigger unable to set variable from select - mysql

Question

I know its asked question ,however I have tried few amendments but to no solution .
My trigger:
BEGIN
DECLARE bookid INT;
DECLARE roomtype varchar(20);
DECLARE amount INT;
DECLARE m_count INT;
DECLARE curr_m varchar(20);
SET #bookid := NEW.id;
SET roomtype := (SELECT title FROM pm_booking_room WHERE id_booking=#bookid);
SET amount := (SELECT amount from pm_booking_payment WHERE id_booking=#bookid);
SET #curr_m:= (MONTHNAME(NOW()));
SET #m_count:= (SELECT count(*) FROM pm_report WHERE month=#curr_m);
INSERT INTO `pm_report`(`month`, `room_type`, `amount`) VALUES(#curr_m,#roomtype,#amount);
END
whwn I check table, it inserts, but only #curr which is month name. Rest it inserts NULL
I tried
SET #roomtype SELECT title FROM pm_booking_room WHERE id_booking=#bookid but still same,NULL .
Also tried SET #roomtype := (SELECT title FROM pm_booking_room WHERE id_booking=#bookid); but still NULL.
I am using PhpMyadmin to create :
Please help.

Answer 1

Please be aware that roomtype and #roomtype are two different variables.
The variables you declare with the local variable DECLARE statement have a scope within the body of one stored routine. They are never spelled with a # sigil.
The user-defined variables with the # sigil have a scope of a MySQL session. You don't need to declare these kinds of variables. Just setting the variable to a value implicitly creates the variable.
You cannot SET roomtype = ... and expect that string to be read from the #roomtype variable. Nor vice-versa.
You appear to declare local variables, so you should use them consistently. But in some cases, your variable names are the same as column names, which will result in ambiguity if you use the variables in SQL statements that also reference tables with those columns. So you should adopt a naming convention to keep them distinct.
BEGIN
DECLARE v_bookid INT;
DECLARE v_roomtype varchar(20);
DECLARE v_amount INT;
DECLARE v_count INT;
DECLARE v_month varchar(20);
SET v_bookid := NEW.id;
SET v_roomtype := (SELECT title FROM pm_booking_room WHERE id_booking=v_bookid);
SET v_amount := (SELECT amount from pm_booking_payment WHERE id_booking=v_bookid);
SET v_month:= (MONTHNAME(NOW()));
SET v_count:= (SELECT count(*) FROM pm_report WHERE month=v_month);
INSERT INTO `pm_report`(`month`, `room_type`, `amount`) VALUES(v_month,v_roomtype,v_amount);
END
(This code is not tested, so apologies if there are any mistakes. It is meant only to demonstrate using non-sigil variables consistently.)