Set multiple variables and case statement in 1 query - sql

Question

I have
table a with columns lot and tid
table b with columns lot and id
table t with columns id and flag
One of my query set variable #ID to the below query whose flag = 'Y'
The 2nd query set variable #ID_Not_Flag to the below query whose flag <> 'Y'
Can I do the below queries (set #ID and #ID_Not_Flag) in 1 query?
SELECT #ID = a.tid
FROM a, b, t
WHERE b.lot = a.lot and b.id =123 and t.id = a.tid and flag = 'Y'
SELECT #ID_Not_Flag = a.tid
FROM a, b, t
WHERE b.lot = a.lot and b.id =123 and t.id = a.tid and flag <> 'Y'
Table a
lot tid
100 1
100 2
Table b
lot id
100 123
Table t
id flag
1 Y
2 N
Desired result from 1 query:
#ID = 1, #ID_Not_Flag = 2
The below query result in #ID = 1, #ID_Not_Flag = NULL
SELECT
#ID = (CASE WHEN flag = 'Y' THEN a.tid END),
#ID_Not_Flag = (CASE WHEN flag <> 'Y' THEN a.tid END)
FROM a, b, t
WHERE b.lot = a.lot and b.id =123 and t.id = a.tid
SELECT #ID,#ID_Not_Flag
Result (not correct):
ID ID_Not_Flag
1 NULL

Answer 1

You can try a pivot table. The first part of the query is just creating temp tables to hold the data.
/*CREATE TEMP TABLES*/
DECLARE #a TABLE ( lot int, tid int)
DECLARE #b TABLE ( lot int, id int)
DECLARE #t TABLE ( id int, flag VARCHAR(1))
INSERT INTO #a (lot, tid) VALUES (100, 1) , (100, 2)
INSERT INTO #b (lot, id) VALUES (100, 123)
INSERT INTO #t (id, flag) VALUES (1, 'Y') , (2, 'N')
/*QUERY*/
SELECT [Y] [#id] ,
[N] [#id_not_flag]
FROM (
SELECT a.lot, a.tid, b.id , t.flag
--,ID = (CASE WHEN flag = 'Y' THEN a.tid END)
--,ID_Not_Flag = (CASE WHEN flag <> 'Y' THEN a.tid END)
FROM #a a
LEFT JOIN #b b
ON a.lot = b.lot
LEFT JOIN #t t
ON t.id = a.tid) AS Src
PIVOT (max(Src.tid) FOR flag in ([Y] , [N])) Pvt

Answer 2

You can just use another join and COALESCE
Example returns 1 2
DECLARE #a Table(lot INT,tid INT);
DECLARE #b Table(lot int ,id INT);
DECLARE #t Table(id INT,flag CHAR);
INSERT INTO #a(lot, tid)
values
(100, 1),
(100, 2);
INSERT INTO #b(lot, id)
values
(100, 123)
INSERT INTO #t(id, flag)
values
(1, 'Y'),
(2, 'N');
--SELECT * FROM #a;
--SELECT * FROM #b;
--SELECT * FROM #t;
DECLARE
#ID INT,
#ID_Not_Flag INT;
SELECT
#ID = COALESCE(ty.id,#ID),
#ID_Not_Flag = COALESCE(tn.id, #ID_Not_Flag )
FROM #b AS b
INNER JOIN #a AS a ON b.lot = a.lot
LEFT OUTER JOIN #t AS ty ON ty.id = a.tid AND ty.flag = 'Y'
LEFT OUTER JOIN #t AS tn ON tn.id = a.tid AND tn.flag = 'N'
WHERE b.id = 123;
SELECT #ID , #ID_Not_Flag ;