How to add IF ELSE by referencing to previous value - sql

Question

I am trying to read my previous value of "OPENSEATING" and store it into the variable #OPENSEATING. For the second query I want it to check first the value of #OPENSEATING if match condition do the below query.
i believe my declaration is correct, is there any syntax error?
DECLARE #OPENSEATING AS BIT
SELECT
'2019-01-31' AS DATE,
(SELECT
THEATRES.OPENSEATING
FROM
SEAT LEFT JOIN THEATRES ON SEAT.ROOMID = THEATRES.ID
LEFT JOIN SHOWTIMES AS B ON THEATRES.ID = B.THEATREID
LEFT JOIN TICKET_ITEMS ON TICKET_ITEMS.SEATNO = SEAT.SEATNO AND B.ID = TICKET_ITEMS.SHOWTIMESID
WHERE
B.ID = A.ID
GROUP BY THEATRES.OPENSEATING) AS #OPENSEATING,
IF(#OPENSEATING =0)
BEGIN
(SELECT
(THEATRES.CAPACITY - COUNT(TICKET_ITEMS.ID)) AS SEATREMAINING
FROM
SEAT LEFT JOIN THEATRES ON SEAT.ROOMID = THEATRES.ID
LEFT JOIN SHOWTIMES ON THEATRES.ID = SHOWTIMES.THEATREID
LEFT JOIN TICKET_ITEMS ON TICKET_ITEMS.SEATNO = SEAT.SEATNO AND SHOWTIMES.ID = TICKET_ITEMS.SHOWTIMESID
WHERE
SHOWTIMES.ID = A.ID
GROUP BY THEATRES.CAPACITY) AS REMAININGSEAT
END
ELSE IF(#OPENSEATING =1)
BEGIN
(SELECT
(THEATRES.CAPACITY - COUNT(TICKET_ITEMS.ID)) AS SEATREMAINING
FROM
SHOWTIMES LEFT JOIN THEATRES ON THEATRES.ID = SHOWTIMES.THEATREID
LEFT JOIN TICKET_ITEMS ON TICKET_ITEMS.SEATNO = SEAT.SEATNO AND SHOWTIMES.ID = TICKET_ITEMS.SHOWTIMESID
WHERE
SHOWTIMES.ID = A.ID
GROUP BY THEATRES.CAPACITY) AS REMAININGSEAT
END
SHOWSCHEDULES.ID AS SHOWSCHEDULE_ID,
A.ID AS SHOWTIME_ID,
A.THEATREID
FROM
SHOWSCHEDULES JOIN SHOWTIMES AS A ON SHOWSCHEDULES.ID = A.SHOWSCHEDULEID
JOIN SHOWLANGUAGES ON A.SHOWLANGUAGEID = SHOWLANGUAGES.ID
WHERE
'2019-01-31' BETWEEN CONVERT(VARCHAR(10), SHOWSCHEDULES.SHOWFROMDATE, 20) AND CONVERT(VARCHAR(10), SHOWSCHEDULES.SHOWTODATE, 20)
AND CONVERT(VARCHAR(8), getdate(), 8) < CONVERT(VARCHAR(10), A.SHOWENDTIME,8)
ORDER BY SHOWBEGINTIME_24 ASC
;
AS SUGGESTED BY #Slava Murygin I tried creating CTE TABLE as below but even this is showing error, what is wrong with my simple cte table. The inner query is working fine.
WITH cte_name (OPENSEATING) AS (
SELECT
(SELECT
THEATRES.OPENSEATING
FROM
SEAT LEFT JOIN THEATRES ON SEAT.ROOMID = THEATRES.ID
LEFT JOIN SHOWTIMES AS B ON THEATRES.ID = B.THEATREID
LEFT JOIN TICKET_ITEMS ON TICKET_ITEMS.SEATNO = SEAT.SEATNO AND B.ID = TICKET_ITEMS.SHOWTIMESID
WHERE
B.ID = A.ID
GROUP BY THEATRES.OPENSEATING) AS OPENSEATING
FROM
SHOWSCHEDULES JOIN SHOWTIMES AS A ON SHOWSCHEDULES.ID = A.SHOWSCHEDULEID
JOIN SHOWLANGUAGES ON A.SHOWLANGUAGEID = SHOWLANGUAGES.ID
WHERE
'2019-01-31' BETWEEN CONVERT(VARCHAR(10), SHOWSCHEDULES.SHOWFROMDATE, 20) AND CONVERT(VARCHAR(10), SHOWSCHEDULES.SHOWTODATE, 20)
AND CONVERT(VARCHAR(8), getdate(), 8) < CONVERT(VARCHAR(10), A.SHOWENDTIME,8)
)

Answer 1

I have made changes to your CTE as:
WITH cte_name (OPENSEATING) AS (
SELECT
THEATRES.OPENSEATING as OPENSEATING
FROM
SEAT LEFT JOIN THEATRES ON SEAT.ROOMID = THEATRES.ID
LEFT JOIN SHOWTIMES AS B ON THEATRES.ID = B.THEATREID
LEFT JOIN TICKET_ITEMS ON TICKET_ITEMS.SEATNO = SEAT.SEATNO AND B.ID = TICKET_ITEMS.SHOWTIMESID
WHERE
B.ID = A.ID
GROUP BY THEATRES.OPENSEATING
)
select openseating from
cte_name, SHOWSCHEDULES JOIN SHOWTIMES AS A ON SHOWSCHEDULES.ID = A.SHOWSCHEDULEID
JOIN SHOWLANGUAGES ON A.SHOWLANGUAGEID = SHOWLANGUAGES.ID
WHERE
'2019-01-31' BETWEEN CONVERT(VARCHAR(10), SHOWSCHEDULES.SHOWFROMDATE, 20) AND CONVERT(VARCHAR(10), SHOWSCHEDULES.SHOWTODATE, 20)
AND CONVERT(VARCHAR(8), getdate(), 8) < CONVERT(VARCHAR(10), A.SHOWENDTIME,8)

Answer 2

You can't do that in one query. You have to get variable in the first query and then use it in IF statement.
If you WANT to use ONLY ONE statement then you have to use CTEs, but it will hide the logic and will be hard to debug.
It might be something like this, but no guarantee it will work, because I have no idea about your business logic and data behind:
;WITH OPENSEATING as (
SELECT THEATRES.OPENSEATING, B.ID
FROM SEAT
LEFT JOIN THEATRES ON SEAT.ROOMID = THEATRES.ID
LEFT JOIN SHOWTIMES AS B ON THEATRES.ID = B.THEATREID
LEFT JOIN TICKET_ITEMS ON TICKET_ITEMS.SEATNO = SEAT.SEATNO AND B.ID = TICKET_ITEMS.SHOWTIMESID
GROUP BY THEATRES.OPENSEATING),
REMAININGSEAT0 as (
SELECT st.ID, (t.CAPACITY - COUNT(ti.ID)) AS SEATREMAINING
FROM SEAT as s
LEFT JOIN THEATRES as t ON s.ROOMID = t.ID
LEFT JOIN SHOWTIMES as st ON t.ID = st.THEATREID
LEFT JOIN TICKET_ITEMS ON ti.SEATNO = s.SEATNO AND st.ID = ti.SHOWTIMESID
GROUP BY t.CAPACITY),
REMAININGSEAT1 as (
SELECT st.ID, (t.CAPACITY - COUNT(ti.ID)) AS SEATREMAINING
FROM SHOWTIMES as st
LEFT JOIN THEATRES as t ON t.ID = st.THEATREID
LEFT JOIN SEAT as s ON s.ROOMID = t.ID
LEFT JOIN TICKET_ITEMS as ti ON ti.SEATNO = s.SEATNO AND st.ID = ti.SHOWTIMESID
GROUP BY t.CAPACITY)
SELECT '2019-01-31' AS DATE
, ss.ID AS SHOWSCHEDULE_ID
, A.ID AS SHOWTIME_ID
, A.THEATREID
, SEATREMAINING = CASE OS.OPENSEATING WHEN 0 THEN RS0.SEATREMAINING ELSE RS1.SEATREMAINING END
FROM SHOWSCHEDULES as ss
INNER JOIN SHOWTIMES AS A ON ss.ID = A.SHOWSCHEDULEID
INNER JOIN SHOWLANGUAGES as SL ON A.SHOWLANGUAGEID = SL.ID
INNER JOIN OPENSEATING as OS ON OS.ID = A.ID
LEFT JOIN REMAININGSEAT0 as RS0 ON RS0.ID = A.ID
LEFT JOIN REMAININGSEAT1 as RS1 ON RS1.ID = A.ID
WHERE '2019-01-31' BETWEEN CONVERT(VARCHAR(10), ss.SHOWFROMDATE, 20) AND CONVERT(VARCHAR(10), ss.SHOWTODATE, 20)
AND CONVERT(VARCHAR(8), getdate(), 8) < CONVERT(VARCHAR(10), A.SHOWENDTIME,8)
ORDER BY SHOWBEGINTIME_24 ASC;