Oracle join query - sql

Question

There are three tables in my db: ITEM_MASTER, PRICE_MASTER and COMP_MASTER.
ITEM_MASTER
STORE_CODE ITEM_CODE ITEM_DESC
011 914004 desccc
PRICE_MASTER
STORE_CODE ITEM_CODE COMP_CODE
011 914004 01
011 914004 02
011 914004 03
011 914004 04
COMP_MASTER
COMP_CODE COMP_DESC STORE_CODE
01 comp1 011
02 comp2 011
03 comp3 011
04 comp4 011
I want to get all these for an ITEM_CODE in a single query.
STORE_CODE ITEM_CODE ITEM_DESC COMP_DESC1 COMP_DESC2 COMP_DESC3 COMP_DESC4
011 914004 desccc comp1 comp2 comp3 comp4
How can I write an oracle SQL query for this?

Answer 1

There are two steps involved to get this output: a join and a pivot.
An example:
First create your sample tables:
SQL> create table item_master (store_code,item_code,item_desc)
2 as
3 select '011', 914004, 'desccc' from dual
4 /
Table created.
SQL> create table price_master (store_code,item_code,comp_code)
2 as
3 select '011', 914004, '01' from dual union all
4 select '011', 914004, '02' from dual union all
5 select '011', 914004, '03' from dual union all
6 select '011', 914004, '04' from dual
7 /
Table created.
SQL> create table comp_master (comp_code,comp_desc,store_code)
2 as
3 select '01', 'comp1', '011' from dual union all
4 select '02', 'comp2', '011' from dual union all
5 select '03', 'comp3', '011' from dual union all
6 select '04', 'comp4', '011' from dual
7 /
Table created.
First step is the join. Here I use ANSI join syntax, but you can use good old Oracle join syntax as well.
SQL> select i.store_code
2 , i.item_code
3 , i.item_desc
4 , c.comp_desc
5 from item_master i
6 inner join price_master p
7 on ( i.store_code = p.store_code
8 and i.item_code = p.item_code
9 )
10 inner join comp_master c
11 on ( p.store_code = c.store_code
12 and p.comp_code = c.comp_code
13 )
14 /
STO ITEM_CODE ITEM_D COMP_
--- ---------- ------ -----
011 914004 desccc comp1
011 914004 desccc comp2
011 914004 desccc comp3
011 914004 desccc comp4
4 rows selected.
The comp description appear below each other, but you want them to be next to each other. To achieve that, you pivot the result set. Note that you have to hard code the number of rows you want to pivot:
SQL> with t as
2 ( select i.store_code
3 , i.item_code
4 , i.item_desc
5 , c.comp_desc
6 , row_number() over (partition by i.store_code,i.item_code order by c.comp_code) rn
7 from item_master i
8 inner join price_master p
9 on ( i.store_code = p.store_code
10 and i.item_code = p.item_code
11 )
12 inner join comp_master c
13 on ( p.store_code = c.store_code
14 and p.comp_code = c.comp_code
15 )
16 )
17 select store_code
18 , item_code
19 , item_desc
20 , max(decode(rn,1,comp_desc)) comp_desc1
21 , max(decode(rn,2,comp_desc)) comp_desc2
22 , max(decode(rn,3,comp_desc)) comp_desc3
23 , max(decode(rn,4,comp_desc)) comp_desc4
24 from t
25 group by store_code
26 , item_code
27 , item_desc
28 /
STO ITEM_CODE ITEM_D COMP_ COMP_ COMP_ COMP_
--- ---------- ------ ----- ----- ----- -----
011 914004 desccc comp1 comp2 comp3 comp4
1 row selected.
Hope this helps.
Regards,
Rob.