Oracle - Rank and transform on columns

Question

I got a sample data as below in this cte_orders. Each row is a order and contains the user_id, zone_code and zone_name.

I need to rank the top 3 zone_code for each user_id, and I need the output be on columns. Like this

|user_id |  top1_zone  |  top2_zone  |  top3_zone  |
|--------+-------------+-------------+-------------+
|1000    |  5555-ABCD  |  4567-ZMNY  |  7888-IXPO  |
|--------+-------------+-------------+-------------+
|9999    |  3456-JJKL  |  7688-HBGT  |  5555-ABCD  |
|--------+-------------+-------------+-------------+

Here's the SQL with the test data and the query that I'm trying. The problem with this query is the result is given a row for each position of the rank.

(
    SELECT 1 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
    SELECT 2 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
    SELECT 3 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
    SELECT 4 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
    SELECT 5 as order_id, '1000' as user_id, '5599' as zone_code, 'HZTR' as zone_name from dual union all
    SELECT 6 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
    SELECT 7 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
    SELECT 8 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
    SELECT 9 as order_id, '1000' as user_id, '1999' as zone_code, 'LNKJ' as zone_name from dual union all
    SELECT 10 as order_id, '1000' as user_id, '5677' as zone_code, 'OPLH' as zone_name from dual union all
    SELECT 11 as order_id, '1000' as user_id, '7888' as zone_code, 'IXPO' as zone_name from dual union all
    SELECT 12 as order_id, '9999' as user_id, '5599' as zone_code, 'HZTR' as zone_name from dual union all
    SELECT 13 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
    SELECT 14 as order_id, '9999' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
    SELECT 15 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
    SELECT 16 as order_id, '9999' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
    SELECT 17 as order_id, '9999' as user_id, '7688' as zone_code, 'HBGT' as zone_name from dual union all
    SELECT 17 as order_id, '9999' as user_id, '7688' as zone_code, 'HBGT' as zone_name from dual union all
    SELECT 18 as order_id, '9999' as user_id, '1566' as zone_code, 'LNOI' as zone_name from dual union all
    SELECT 19 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
    SELECT 20 as order_id, '9999' as user_id, '7654' as zone_code, 'NNJJ' as zone_name from dual union all
    SELECT 21 as order_id, '9999' as user_id, '4433' as zone_code, 'NHJE' as zone_name from dual union all
    SELECT 22 as order_id, '9999' as user_id, '4111' as zone_code, 'ABHJ' as zone_name from dual

)

select 
    user_id,
    CASE WHEN rank_zones = 1 then zone_concat end as top1_zone,
    CASE WHEN rank_zones = 2 then zone_concat end as top2_zone,
    CASE WHEN rank_zones = 3 then zone_concat end as top3_zone
    from

( 
    select  
        user_id, 
        zone_code||'-'||zone_name as zone_concat,
        row_number() over (partition by user_id order by count(*) desc) rank_zones 
    from cte_orders
    group by
        user_id,
        zone_code||'-'||zone_name

)
where rank_zones <= 3

group by 
    user_id,
    CASE WHEN rank_zones = 1 then zone_concat end,
    CASE WHEN rank_zones = 2 then zone_concat end,
    CASE WHEN rank_zones = 3 then zone_concat end
order by user_id;

The output that i getting

|user_id |  top1_zone  |  top2_zone  |  top3_zone  |
|--------+-------------+-------------+-------------+
|1000    |  5555-ABCD  |    (null)   |    (null)   |
|--------+-------------+-------------+-------------+
|1000    |    (null)   |  4567-ZMNY  |    (null)   |
|--------+-------------+-------------+-------------+
|1000    |    (null)   |    (null)   |  7888-IXPO  |
|--------+-------------+-------------+-------------+
|9999    |  3456-JJKL  |    (null)   |    (null)   |
|--------+-------------+-------------+-------------+
|9999    |    (null)   |  7688-HBGT  |    (null)   |
|--------+-------------+-------------+-------------+
|9999    |    (null)   |    (null)   |  5555-ABCD  |
|--------+-------------+-------------+-------------+

How can i fix my query to get one row for each user_id without the nulls?

Answer 1

You can use oracle pivot as below:

 with cte_orders as(
     SELECT 1 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 2 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
     SELECT 3 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 4 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 5 as order_id, '1000' as user_id, '5599' as zone_code, 'HZTR' as zone_name from dual union all
     SELECT 6 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
     SELECT 7 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
     SELECT 8 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 9 as order_id, '1000' as user_id, '1999' as zone_code, 'LNKJ' as zone_name from dual union all
     SELECT 10 as order_id, '1000' as user_id, '5677' as zone_code, 'OPLH' as zone_name from dual union all
     SELECT 11 as order_id, '1000' as user_id, '7888' as zone_code, 'IXPO' as zone_name from dual union all
     SELECT 12 as order_id, '9999' as user_id, '5599' as zone_code, 'HZTR' as zone_name from dual union all
     SELECT 13 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
     SELECT 14 as order_id, '9999' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 15 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
     SELECT 16 as order_id, '9999' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 17 as order_id, '9999' as user_id, '7688' as zone_code, 'HBGT' as zone_name from dual union all
     SELECT 17 as order_id, '9999' as user_id, '7688' as zone_code, 'HBGT' as zone_name from dual union all
     SELECT 18 as order_id, '9999' as user_id, '1566' as zone_code, 'LNOI' as zone_name from dual union all
     SELECT 19 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
     SELECT 20 as order_id, '9999' as user_id, '7654' as zone_code, 'NNJJ' as zone_name from dual union all
     SELECT 21 as order_id, '9999' as user_id, '4433' as zone_code, 'NHJE' as zone_name from dual union all
     SELECT 22 as order_id, '9999' as user_id, '4111' as zone_code, 'ABHJ' as zone_name from dual
 
 ),
 cte as(select  
         user_id, 
         zone_code||'-'||zone_name as zone_concat,
         row_number() over (partition by user_id order by count(*) desc ) rank_zones 
     from cte_orders
     group by
         user_id,
         zone_code||'-'||zone_name)
 
 select user_id,"1" top1_zone, "2" top2_zone, "3" top3_zone
 from cte 
 PIVOT (
   MAX(ZONE_CONCAT) FOR rank_zones IN (1,2,3)
 )
 

Output:

USER_ID	TOP1_ZONE	TOP2_ZONE	TOP3_ZONE
1000	5555-ABCD	4567-ZMNY	5599-HZTR
9999	3456-JJKL	5555-ABCD	7688-HBGT

db<>fiddle here

Or you can use decode in aggregation with group by:

 with cte_orders as(
     SELECT 1 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 2 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
     SELECT 3 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 4 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 5 as order_id, '1000' as user_id, '5599' as zone_code, 'HZTR' as zone_name from dual union all
     SELECT 6 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
     SELECT 7 as order_id, '1000' as user_id, '4567' as zone_code, 'ZMNY' as zone_name from dual union all
     SELECT 8 as order_id, '1000' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 9 as order_id, '1000' as user_id, '1999' as zone_code, 'LNKJ' as zone_name from dual union all
     SELECT 10 as order_id, '1000' as user_id, '5677' as zone_code, 'OPLH' as zone_name from dual union all
     SELECT 11 as order_id, '1000' as user_id, '7888' as zone_code, 'IXPO' as zone_name from dual union all
     SELECT 12 as order_id, '9999' as user_id, '5599' as zone_code, 'HZTR' as zone_name from dual union all
     SELECT 13 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
     SELECT 14 as order_id, '9999' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 15 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
     SELECT 16 as order_id, '9999' as user_id, '5555' as zone_code, 'ABCD' as zone_name from dual union all
     SELECT 17 as order_id, '9999' as user_id, '7688' as zone_code, 'HBGT' as zone_name from dual union all
     SELECT 17 as order_id, '9999' as user_id, '7688' as zone_code, 'HBGT' as zone_name from dual union all
     SELECT 18 as order_id, '9999' as user_id, '1566' as zone_code, 'LNOI' as zone_name from dual union all
     SELECT 19 as order_id, '9999' as user_id, '3456' as zone_code, 'JJKL' as zone_name from dual union all
     SELECT 20 as order_id, '9999' as user_id, '7654' as zone_code, 'NNJJ' as zone_name from dual union all
     SELECT 21 as order_id, '9999' as user_id, '4433' as zone_code, 'NHJE' as zone_name from dual union all
     SELECT 22 as order_id, '9999' as user_id, '4111' as zone_code, 'ABHJ' as zone_name from dual
 
 ),
 cte as(select  
         user_id, 
         zone_code||'-'||zone_name as zone_concat,
         row_number() over (partition by user_id order by count(*) desc ) rank_zones 
     from cte_orders
     group by
         user_id,
         zone_code||'-'||zone_name)
 
 select user_id,
   max(decode(rank_zones,1,ZONE_CONCAT)) top1_zone,
   max(decode(rank_zones,2,ZONE_CONCAT)) top2_zone,
   max(decode(rank_zones,3,ZONE_CONCAT)) top3_zone
 from cte 
 group by user_id

Output:

USER_ID	TOP1_ZONE	TOP2_ZONE	TOP3_ZONE
1000	5555-ABCD	4567-ZMNY	5599-HZTR
9999	3456-JJKL	5555-ABCD	7688-HBGT

db<>fiddle here