Oracle SQL assign if less than configured parameter - sql

Question

I have the below 2 tables:
assigned
VK
PC
A
B
RANK
VK1
PC1
A1
null
1
VK2
PC1
A1
A2
2
VK3
PC1
A2
null
3
VK4
PC1
A2
null
4
VK5
PC1
null
A1
5
VK6
PC1
null
A2
6
res
PC
A
MAXI
PC1
A1
2
PC1
A2
2
I would like to have the below desired output, based on this logic:
If B!=A, then assign B to C if the count of the value in B in the preceding rows order by rank is less than 'MAXI' in table res for that 'PC' and 'A'. If B=A or B is null, assign A to C.
After updating setting column C with the logic in point 1, if the count of any 'A's is less than 'MAXI' in table res, update the first null value to that 'A' until the count of 'A's is equal than 'MAXI' in res. Similarly, if the count of 'A's exceed 'MAXI' for any of the 'A's, set C to null the lowest assigned ranks until the condition is met.
Desired output:
VK
PC
A
B
RANK
C
VK1
PC1
A1
null
1
A1
VK2
PC1
A1
A2
2
A2
VK3
PC1
A2
null
3
A2
VK4
PC1
A2
null
4
A1
VK5
PC1
null
A1
5
null
VK6
PC1
null
A2
6
null
NOTE: row 4 was assigned to A1 instead of A2 because row 2 had to be assigned to A2 and thus row 4 exceeded the quota for A2. Quota for A1 was still 1 (less than 2), so could be assigned to A1. For row 5, there were already 2 A1s assigned (row 1 and 4), so the quota was exceeded and C had to be null.
EDIT: this is what I've tried so far.
with assigned (vk, pc, a, b, r) as(
select 'VK1', 'PC1', 'A1', null, 1 from dual union all
select 'VK2', 'PC1', 'A1', 'A2', 2 from dual union all
select 'VK3', 'PC1', 'A2', null, 3 from dual union all
select 'VK4', 'PC1', 'A2', null, 4 from dual union all
select 'VK5', 'PC1', null, 'A1', 5 from dual union all
select 'VK6', 'PC1', null, 'A2', 6 from dual),
res(pc, a, maxi) as(
select 'PC1', 'A1', 2 from dual union all
select 'PC1', 'A2', 2 from dual
)
, aux AS (
SELECT
a.*,
coalesce(a.b, a.a) d,
COUNT(coalesce(a.b, a.a)) OVER(
PARTITION BY coalesce(a.b, a.a)
ORDER BY
r
) i,
b.maxi
FROM
assigned a
LEFT JOIN res b ON ( b.pc = a.pc
AND b.a = a.a )
)
SELECT
a.*,
case
when i<=maxi then d
else a end c
FROM
aux a
order by r;

Answer 1

Your logic appears to be something like this:
WITH res_rows ( pc, a, maxi, total ) AS (
SELECT pc, a, maxi, SUM( maxi ) OVER( PARTITION BY pc )
FROM res
WHERE maxi > 0
UNION ALL
SELECT pc, a, maxi - 1, total FROM res_rows WHERE maxi > 1
),
p1 ( vk, pc, a, b, r, c, rn, pc_r ) AS (
SELECT a.*,
COALESCE(b, a),
ROW_NUMBER() OVER (PARTITION BY pc, COALESCE(b, a) ORDER BY r),
ROW_NUMBER() OVER (PARTITION BY pc ORDER BY r)
FROM assigned a
),
p2 ( vk, pc, a, b, r, c, rn ) AS (
SELECT p1.vk,
p1.pc,
p1.a,
p1.b,
p1.r,
r.a,
CASE
WHEN r.a IS NULL
THEN ROW_NUMBER() OVER (
PARTITION BY p1.pc
ORDER BY CASE WHEN r.a IS NULL THEN p1.r END
)
ELSE p1.rn
END
FROM p1
LEFT OUTER JOIN res_rows r
ON ( p1.pc = r.pc AND p1.c = r.a AND p1.rn = r.maxi AND p1.pc_r <= total )
),
missing ( pc, a, rn ) AS (
SELECT pc,
a,
ROW_NUMBER() OVER ( PARTITION BY pc ORDER BY ROWNUM )
FROM (
SELECT pc, a, maxi FROM res_rows
MINUS
SELECT pc, c, rn FROM p2 WHERE c IS NOT NULL
)
)
SELECT p2.vk,
p2.pc,
p2.a,
p2.b,
p2.r,
COALESCE( m.a, p2.c ) AS c
FROM p2
LEFT OUTER JOIN missing m
ON ( p2.pc = m.pc AND p2.c IS NULL AND p2.rn = m.rn )
ORDER BY r
Which outputs:
VK
PC
A
B
R
C
VK1
PC1
A1
1
A1
VK2
PC1
A1
A2
2
A2
VK3
PC1
A2
3
A2
VK4
PC1
A2
4
A1
VK5
PC1
A1
5
VK6
PC1
A2
6
db<>fiddle here