Oracle sql query - sql

Question

I am dealing with tables which (for the purposes of displaying here) look like the following:
A
A_ID | Clob_Col
1 | value
2 | value
3 | null
4 | value
5 | null
6 | value
7 | value
8 | null
9 | value
10 | value
B
B_ID |A_ID | C_ID
10 | 1 | 20
11 | 2 | 20
12 | 6 | 21
13 | 7 | 22
14 | 8 | 22
15 | 9 | 23
C
C_ID
20
21
22
23
24
25
(All tables have more columns)
I wish to write a query which will return values from all three tables but exclude records where certain values match those in Table C (NOT IN).
My problem is to return the values from Table A which do not link to Table B when using a NOT IN clause on Table C.
Example:
SELECT a.A_ID, a.Clob_Col, b.B_ID, c.C_ID
from A a
LEFT JOIN B b on a.A_ID=b.A_ID
LEFT JOIN C c on b.C_ID=c.C_ID
WHERE a.AID >= 2
AND a.AID <= 7
AND c.C_ID NOT IN (22, 23, 24)
The last line - c.C_ID NOT IN (22, 23, 24) - will leave us with the following records in the B table: b_BID = 10,11 or 12
In turn, these link to the following records in Table A: a.ID = 1,2 and 6.
The first clause - a.AID >= 2 AND a.AID <= 7 - further restricts our final result to a.ID = 2 and 6.
The final result will look like:
A_ID |Clob_Col |B_ID |C_ID
2 |value |11 |20
6 |value |12 |21
But I also want to return the A table records which don't link to Table B - a.ID 3, 4 and 5
So I expect my results to be
A_ID |Clob_Col |B_ID |C_ID
2 |value |11 |20
3 |null |null |null
4 |value |null |null
5 |null |null |null
6 |value |12 |21
Note: The reason I included the Clob value is that someone suggested selecting all records and then performing a MINUS operation on the records where c.C_ID IN (22, 23, 24).
This seemed reasonable however Oracle does not allow MINUS operation where Clob columns are involved.

Answer 1

I think you forgot to use "on" clause for join. You can try this :
SELECT a.A_ID, a.Clob_Col, b.B_ID, c.C_ID
from A a
LEFT JOIN B b on a.A_ID=b.A_ID
LEFT JOIN C c on b.C_ID=c.C_ID
WHERE a.A_ID between 2 and 7
AND c.C_ID NOT IN (22, 23, 24)
Hope it will work.

Answer 2

Include what your joining on and also you can use BETWEEN for the first WHERE clause.
Also i would use INNER JOINS rather then LEFT as per your data.
SELECT a.A_ID, a.Clob_Col, b.B_ID, c.C_ID
FROM A a
INNER JOIN B b ON a.A_ID = b.B_ID
INNER JOIN C c ON b.C_ID = c.C_ID
WHERE a.AID BETWEEN 2 AND 7
AND c.C_ID NOT IN (22, 23, 24)

Answer 3

I think this does what you're after:
with a as (select 1 a_id, 'val1' clob_col from dual union all
select 2 a_id, 'val2' clob_col from dual union all
select 3 a_id, null clob_col from dual union all
select 4 a_id, 'val4' clob_col from dual union all
select 5 a_id, null clob_col from dual union all
select 6 a_id, 'val6' clob_col from dual union all
select 7 a_id, 'val7' clob_col from dual union all
select 8 a_id, null clob_col from dual union all
select 9 a_id, 'val9' clob_col from dual union all
select 10 a_id, 'val10' clob_col from dual),
b as (select 10 b_id, 1 a_id, 20 c_id from dual union all
select 11 b_id, 2 a_id, 20 c_id from dual union all
select 12 b_id, 6 a_id, 21 c_id from dual union all
select 13 b_id, 7 a_id, 22 c_id from dual union all
select 14 b_id, 8 a_id, 22 c_id from dual union all
select 15 b_id, 9 a_id, 23 c_id from dual),
c as (select 20 c_id from dual union all
select 21 c_id from dual union all
select 22 c_id from dual union all
select 23 c_id from dual union all
select 24 c_id from dual union all
select 25 c_id from dual)
select a.a_id, a.clob_col, b.b_id, c.c_id
from a
left outer join b on (a.a_id = b.a_id)
left outer join c on (b.c_id = c.c_id)
where a.a_id between 2 and 7
and (c.c_id not in (22, 23, 24) or c.c_id is null)
order by a.a_id;
A_ID CLOB_COL B_ID C_ID
---------- -------- ---------- ----------
2 val2 11 20
3
4 val4
5
6 val6 12 21
and if c_id is 27 for a_id = 6 in the b table:
A_ID CLOB_COL B_ID C_ID
---------- -------- ---------- ----------
2 val2 11 20
3
4 val4
5
6 val6 12
You have to take account of the fact that c_id could be null, as well as not being in the set of values being excluded.
ETA: Thanks to Ponder Stibbons' suggestion in the comments, if you didn't want the row to be displayed where a.a_id = b.a_id matches but there isn't a match on b.c_id = c.c_id, then changing the or c.c_id is null to or b.c_id is null removes that row:
with a as (select 1 a_id, 'val1' clob_col from dual union all
select 2 a_id, 'val2' clob_col from dual union all
select 3 a_id, null clob_col from dual union all
select 4 a_id, 'val4' clob_col from dual union all
select 5 a_id, null clob_col from dual union all
select 6 a_id, 'val6' clob_col from dual union all
select 7 a_id, 'val7' clob_col from dual union all
select 8 a_id, null clob_col from dual union all
select 9 a_id, 'val9' clob_col from dual union all
select 10 a_id, 'val10' clob_col from dual),
b as (select 10 b_id, 1 a_id, 20 c_id from dual union all
select 11 b_id, 2 a_id, 20 c_id from dual union all
select 12 b_id, 6 a_id, 27 c_id from dual union all
select 13 b_id, 7 a_id, 22 c_id from dual union all
select 14 b_id, 8 a_id, 22 c_id from dual union all
select 15 b_id, 9 a_id, 23 c_id from dual),
c as (select 20 c_id from dual union all
select 21 c_id from dual union all
select 22 c_id from dual union all
select 23 c_id from dual union all
select 24 c_id from dual union all
select 25 c_id from dual)
select a.a_id, a.clob_col, b.b_id, c.c_id
from a
left outer join b on (a.a_id = b.a_id)
left outer join c on (b.c_id = c.c_id)
where a.a_id between 2 and 7
and (c.c_id not in (22, 23, 24) or b.c_id is null)
order by a.a_id;