values from table that not exist in another (by seperate group column) - oracle

Question

This qes is about oracle db.
I have a table (T1) with several columns:
group
id
price
A
1
50
A
5
40
B
4
54
C
1
33
C
6
33
D
5
13
D
3
4
And another table (T2) with 2 columns:
id
description
1
aaa
2
bbb
3
ccc
4
ddd
5
eee
6
fff
7
ggg
The Id in this table (t2) is unique.
the connection between the two tables is by the "id" column.
I need to check for each (!) Group in T1 (A, B, C, D),
which of the "id" from T2 - not found for this group in T1,
and the result needs to be: group + id (that does not exist in this group)
for the example on the above tables, I expected to get this result:
group
id
A
2
A
3
A
4
A
6
A
7
B
1
B
2
B
3
B
5
B
6
B
7
C
2
C
3
C
4
C
5
C
7
D
1
D
2
D
4
D
6
D
7
Thank You!

Answer 1

In Oracle you may use partitioned join
with a(grp, id, price) as (
select 'A', 1, 50 from dual union all
select 'A', 5, 40 from dual union all
select 'B', 4, 54 from dual union all
select 'C', 1, 33 from dual union all
select 'C', 6, 33 from dual union all
select 'D', 5, 13 from dual union all
select 'D', 3, 4 from dual
)
, b (id, descr) as (
select 1, 'aaa' from dual union all
select 2, 'bbb' from dual union all
select 3, 'ccc' from dual union all
select 4, 'ddd' from dual union all
select 5, 'eee' from dual union all
select 6, 'fff' from dual union all
select 7, 'ggg' from dual
)
select
grp
, id
from a
partition by (grp)
right join b
using (id)
where a.price is null
order by grp, id
GRP | ID
:-- | -:
A | 2
A | 3
A | 4
A | 6
A | 7
B | 1
B | 2
B | 3
B | 5
B | 6
B | 7
C | 2
C | 3
C | 4
C | 5
C | 7
D | 1
D | 2
D | 4
D | 6
D | 7
db<>fiddle here

Answer 2

The idea here is to create all possible record combinations by using a Cartesian join and then match all groups and select non existing via left join and not null
create table T1 (c1 varchar2(10), c2 number(10), c3 number(10))
insert into T1 values('A', 1, 50);
insert into T1 values('A', 5, 40);
insert into T1 values('B', 4 , 54);
insert into T1 values('C', 1, 33);
insert into T1 values('C', 6, 33);
insert into T1 values('D', 5, 13);
insert into T1 values('D', 3, 4);
create table T2 (c6 number(10), c7 varchar2(10))
insert into T2 values( 1, 'aaa');
insert into T2 values( 2, 'bbb');
insert into T2 values( 3, 'ccc');
insert into T2 values( 4, 'ddd');
insert into T2 values( 5, 'eee');
insert into T2 values( 6, 'fff');
insert into T2 values( 7, 'ggg');
SELECT tx.c1, tx.c6, ty.c1
FROM
(select c1, c6
from
(select distinct c1 from T1) ta,
(select distinct c6 from T2) tb) tx -- tx is the cartisian product
left join
(select c1, c2 from T1 group by c1, c2) ty
on tx.c1 = ty.c1 and tx.c6 = ty.c2
WHERE
ty.c1 is null
ORDER BY 1, 2
This gets you exactly what you're looking for.
Tested and verified

Answer 3

First, find all the possible combinations, then determine which of them don't exist:
WITH cteCombinations
AS (SELECT DISTINCT T1."group", T2.ID
FROM T1
CROSS JOIN T2)
SELECT c."group", c.ID
FROM cteCombinations c
LEFT OUTER JOIN T1
ON T1.ID = c.ID AND
T1."group" = c."group"
WHERE T1.ID IS NULL
ORDER BY c."group", c.ID
The CTE (Common Table Expression) uses a CROSS JOIN to find all of the unique combinations of group and ID; then the LEFT OUTER JOIN is used to determine which of the combinations don't exist in T1.
Another way to do it is:
WITH cteCombinations
AS (SELECT DISTINCT T1."group", T2.ID
FROM T1
CROSS JOIN T2)
SELECT c."group", c.ID
FROM cteCombinations c
WHERE (c."group", c.ID) NOT IN (SELECT "group", ID
FROM T1)
ORDER BY c."group", c.ID
Here we use the same CTE to generate the possible combinations, but instead of a LEFT OUTER JOIN we use a NOT IN comparison to determine which of the combinations are not present in table T1.
db<>fiddle here