Combining two columns based on match in other colums in two tables - sql

Question

I have two tables, each containing two identical columns and one column unique for that table. What I need to do is combine those tables, with combinations of those unique columns for each matching pair of identical columns as result. Example of what I mean:
ACC ACTION PRIORITY ACC ACTION TARGET
A 1 10 A 1 i
A 2 15 A 1 j
A 3 25 A 3 k
B 3 101 B NULL l
B 4 102 B 4 m
B 5 103 B 1 n
ACC and ACTION are columns in both tables. ORDER is unique for the left one, TARGET for the right one. I need to get combinations of ORDER and TARGET on rows where ACC and ACTION match - for example when ACC is A and ACTION is 1, PRIORITY is 10, and TARGET is I or j, therefore combinations would be "10 I" and "10 j".
Also, when ACTION is null in right table, there should be row with the top PRIORITY on that TARGET.
So, expected result:
PRIORITY TARGET
10 i
10 j
25 k
102 m
103 l
Any attempt to do a correct JOIN or so failed from my side.
What I tried:
INSERT INTO #RESULT(TARGET, PRIORITY)
SELECT R.TARGET, MAX(L.PRIORITY)
FROM LEFT_TABLE L INNER JOIN RIGHT_TABLE R
ON L.ACC=R.ACC AND (L.ACTION = R.ACTION OR R.ACTION IS NULL);
But it gives an error. Grouping by TARGET does not make the right output, though.

Answer 1

I used UNION to solve this
SELECT priority, t.target
FROM prio p
JOIN target t ON p.acc = t.acc AND t.action = p.action
UNION
SELECT priority, t.target
FROM prio p
JOIN target t ON p.acc = t.acc AND t.action is null
AND p.priority = (SELECT MAX(priority) FROM prio)

Answer 2

See if this works. I did not test it.
DECLARE #L TABLE(ACC NVARCHAR(10),Action INT,Priority INT)
INSERT #L (ACC,Action,Priority) VALUES ('A',1,10),('A',2,15),('A',3,25),('B',4,101),('B',5,102),('B',6,103)
DECLARE #R TABLE(ACC NVARCHAR(10),Action INT,Target NVARCHAR(10))
INSERT #R (ACC,Action,Target) VALUES ('A',1,'i'),('A',1,'j'),('A',3,'k'),('B',NULL,'l'),('B',4,'m'),('B',1,'n')
SELECT
Target = MAX(R.Target),
Priority = MAX(L.Priority)
FROM
#L L
INNER JOIN #R R ON R.ACC=L.Acc AND (R.ACTION=L.Action OR R.Action IS NULL)
GROUP BY
L.ACC,
L.Action
ORDER BY
MAX(L.Priority)

Answer 3

You can do it like this:
Sample data
create table a
(
acc nvarchar(50),Action1 int, priority1 int)
create table b (acc nvarchar(50),action1 int, target1 nvarchar(50)
)
insert into a
values
('A',1, 10 ),
('A',2, 15 ),
('A',3, 25 ),
('B',3, 101),
('B',4, 102),
('B',5, 103)
insert into dbo.b
values
('A',1,'i'),
('A',1,'j'),
('A',3,'k'),
('B',null,'l'),
('B',4,'m'),
('B',1,'n')
SQL
with data1 as (
select acc,case when action1 is null then maxaction1 else action1 end as action1,target1 from (
select * from dbo.b a
cross apply (select MAX(action1) as MaxAction1 from dbo.a b where a.acc = b.acc ) x
)z
)
select priority1,target1 from data1 a inner join dbo.a b on a.acc = b.acc and a.action1 = b.Action1
Update
Just saw that you wrote you want it on Priority. Then you can do it like this:
SQL Code Update
with data1 as (
select * from (
select y.acc,y.target1,COALESCE(y.action1,c.action1) as Action1 from (
select * from dbo.b a
cross apply (select MAX(priority1) as MaxP from dbo.a b where a.acc = b.acc ) x
)y inner join dbo.a c on c.priority1 = MaxP
)z
)
select priority1,target1 from data1 a inner join dbo.a b on a.acc = b.acc and a.action1 = b.Action1
Result

Answer 4

You can try this:
WITH
tTable1
AS ( SELECT ACC
, [ACTION]
, [PRIORITY]
FROM ( VALUES ('A', 1, 10 )
, ('A', 2, 15 )
, ('A', 3, 25 )
, ('B', 3, 101)
, ('B', 4, 102)
, ('B', 5, 103)
) tTable1(ACC, [ACTION], [PRIORITY])
)
, tTable2
AS ( SELECT ACC
, [ACTION]
, [TARGET]
FROM ( VALUES ('A', 1 , 'i')
, ('A', 1 , 'j')
, ('A', 3 , 'k')
, ('B', NULL, 'l')
, ('B', 4 , 'm')
, ('B', 1 , 'n')
) tTable1(ACC, [ACTION], [TARGET])
)
, tTable1Max
AS ( SELECT ACC
, [PRIORITY] = MAX([PRIORITY])
FROM tTable1
GROUP BY ACC
)
, tResult
AS ( SELECT [PRIORITY] = CASE WHEN tTable2.[ACTION] IS NOT NULL
THEN tTable1.[PRIORITY]
ELSE tTable1Max.[PRIORITY]
END
, tTable2.[TARGET]
FROM tTable2
LEFT JOIN tTable1 ON tTable1.ACC = tTable2.ACC
AND tTable1.[ACTION] = tTable2.[ACTION]
OUTER APPLY ( SELECT [PRIORITY]
FROM tTable1Max
WHERE tTable1Max.ACC = tTable2.ACC
) tTable1Max
)
SELECT *
FROM tResult
WHERE [PRIORITY] IS NOT NULL
ORDER BY [PRIORITY]