Multiple left-outer join results in duplicated rows - sql

Question

I have a big table having Incidents. With this I want to attach values from Incident Attachment and Incident Comments. I have used Left outer join as there may or may not be any comments OR attachment for a Incident.
Now when I use multiple outer join i get duplicated rows.
There is a incidentID value that is common for all the tables
INC1 ATT1 COMMENT1
INC1 ATT1 COMMENT2
INC1 ATT2 COMMENT1
INC1 ATT2 COMMENT2
But actually the output should be:
INC1 ATT1 COMMENT1
INC1 ATT2 COMMENT2
so that the attachment and the comment values are independent when attaching themselves to the incident table.
select inc,att.attname,comment.commenttext
from inc
left outer join att inc.incidentID=att.incidentID
left outer join comment inc.incidentID=comment .incidentID
Is this possible?

Answer 1

One of the things I'm taking away from your responses so far is that, for a given incident, there's no direct relationship between its attachments and its comments.
If I understand that correctly, you want to treat an incident as a simple "container" for attachments and comments, and you just want a listing of each. Which
attachment happens to appear in the same row as a particular comment is incidental to you.
TEST DATA:
SQL> CREATE TABLE inc (incidentid NUMBER, incname VARCHAR2(20));
Table created.
SQL> INSERT INTO inc VALUES (1,'incident 1');
1 row created.
SQL> INSERT INTO inc VALUES (2,'incident 2');
1 row created.
SQL> CREATE TABLE att (att_id NUMBER, incidentid NUMBER, attname VARCHAR2(20));
Table created.
SQL> INSERT INTO att VALUES (101, 1, 'attachment 1');
1 row created.
SQL> INSERT INTO att VALUES (102, 1, 'attachment 2');
1 row created.
SQL> INSERT INTO att VALUES (103, 1, 'attachment 3');
1 row created.
SQL> INSERT INTO att VALUES (104, 1, 'attachment 4');
1 row created.
SQL> INSERT INTO att VALUES (105, 1, 'attachment 5');
1 row created.
SQL> INSERT INTO att VALUES (110, 2, 'attachment A');
1 row created.
SQL> INSERT INTO att VALUES (111, 2, 'attachment B');
1 row created.
SQL> INSERT INTO att VALUES (112, 2, 'attachment C');
1 row created.
SQL> CREATE TABLE comments (comment_id NUMBER, incidentid NUMBER, commenttext VARCHAR2(20));
Table created.
SQL> INSERT INTO comments VALUES (201, 1, 'first comment');
1 row created.
SQL> INSERT INTO comments VALUES (202, 1, 'second comment');
1 row created.
SQL> INSERT INTO comments VALUES (203, 1, 'third comment');
1 row created.
PROPOSED QUERY:
SQL> WITH a AS (
2 SELECT att.incidentid
3 , COUNT(att.att_id) rows_per_incident
4 FROM att
5 GROUP BY att.incidentid
6 UNION ALL
7 SELECT comments.incidentid
8 , COUNT(comments.comment_id) rows_per_incident
9 FROM comments
10 GROUP BY comments.incidentid
11 )
12 , b AS (
13 SELECT inc.incidentid
14 , inc.incname
15 , ROW_NUMBER()
16 OVER (PARTITION BY inc.incidentid ORDER BY NULL) row_num
17 FROM inc
18 , (SELECT ROWNUM multiplier FROM DUAL CONNECT BY LEVEL <= (SELECT MAX(rows_per_incident) FROM a))
19 )
20 , c AS (
21 SELECT att.att_id
22 , att.incidentid
23 , att.attname
24 , ROW_NUMBER()
25 OVER (PARTITION BY att.incidentid ORDER BY att.att_id) att_rn
26 FROM att
27 )
28 , d AS (
29 SELECT comments.comment_id
30 , comments.incidentid
31 , comments.commenttext
32 , ROW_NUMBER()
33 OVER (PARTITION BY comments.incidentid ORDER BY comments.comment_id) comm_rn
34 FROM comments
35 )
36 , e AS (
37 SELECT c.incidentid
38 , c.att_id
39 , c.attname
40 , c.att_rn rn
41 , d.comment_id
42 , d.commenttext
43 FROM c
44 , d
45 WHERE c.incidentid = d.incidentid (+)
46 AND c.att_rn = d.comm_rn (+)
47 UNION ALL
48 SELECT TO_NUMBER(NULL) incidentid
49 , TO_NUMBER(NULL) att_id
50 , NULL attname
51 , d.comm_rn rn
52 , d.comment_id
53 , d.commenttext
54 FROM d
55 WHERE NOT EXISTS (SELECT NULL
56 FROM c
57 WHERE c.incidentid = d.incidentid
58 AND c.att_rn = d.comm_rn)
59 )
60 , f AS (
61 SELECT b.incidentid
62 , b.incname
63 , b.row_num
64 , e.att_id
65 , e.attname
66 , e.comment_id
67 , e.commenttext
68 FROM b
69 LEFT OUTER JOIN e ON b.incidentid = e.incidentid
70 AND b.row_num = e.rn
71 )
72 SELECT f.incidentid
73 , f.incname
74 , f.att_id
75 , f.attname
76 , f.comment_id
77 , f.commenttext
78 FROM f
79 WHERE NOT (f.att_id IS NULL AND f.comment_id IS NULL)
80 ORDER BY f.incidentid
81 , f.row_num
82 ;
INCIDENTID INCNAME ATT_ID ATTNAME COMMENT_ID COMMENTTEXT
---------- -------------------- ---------- -------------------- ---------- --------------------
1 incident 1 101 attachment 1 201 first comment
1 incident 1 102 attachment 2 202 second comment
1 incident 1 103 attachment 3 203 third comment
1 incident 1 104 attachment 4
1 incident 1 105 attachment 5
2 incident 2 110 attachment A
2 incident 2 111 attachment B
2 incident 2 112 attachment C
8 rows selected.
SQL>