Get distinct rows based on priority? - sql

Question

I have a table as below.i am using oracle 10g.
TableA
------
id status
---------------
1 R
1 S
1 W
2 R
i need to get distinct ids along with their status. if i query for distinct ids and their status i get all 4 rows.
but i should get only 2. one per id.
here id 1 has 3 distinct statuses. here i should get only one row based on priority.
first priority is to 'S' , second priority to 'W' and third priority to 'R'.
in my case i should get two records as below.
id status
--------------
1 S
2 R
How can i do that? Please help me.
Thanks!

Answer 1

select
id,
max(status) keep (dense_rank first order by instr('SWR', status)) as status
from TableA
group by id
order by 1
fiddle

Answer 2

select id , status from (
select TableA.*, ROW_NUMBER()
OVER (PARTITION BY TableA.id ORDER BY DECODE(
TableA.status,
'S',1,
'W',2,
'R',3,
4)) AS row_no
FROM TableA)
where row_no = 1

Answer 3

This is first thing i would do, but there may be a better way.
Select id, case when status=1 then 'S'
when status=2 then 'W'
when status=3 then 'R' end as status
from(
select id, max(case when status='S' then 3
when status='W' then 2
when status='R' then 1
end) status
from tableA
group by id
);

Answer 4

To get it done you can write a similar query:
-- sample of data from your question
SQL> with t1(id , status) as (
2 select 1, 'R' from dual union all
3 select 1, 'S' from dual union all
4 select 1, 'W' from dual union all
5 select 2, 'R' from dual
6 )
7 select id -- actual query
8 , status
9 from ( select id
10 , status
11 , row_number() over(partition by id
12 order by case
13 when upper(status) = 'S'
14 then 1
15 when upper(status) = 'W'
16 then 2
17 when upper(status) = 'R'
18 then 3
19 end
20 ) as rn
21 from t1
22 ) q
23 where q.rn = 1
24 ;
ID STATUS
---------- ------
1 S
2 R

Answer 5

select id,status from
(select id,status,decode(status,'S',1,'W',2,'R',3) st from table) where (id,st) in
(select id,min(st) from (select id,status,decode(status,'S',1,'W',2,'R',3) st from table))

Answer 6

Something like this???
SQL> with xx as(
2 select 1 id, 'R' status from dual UNION ALL
3 select 1, 'S' from dual UNION ALL
4 select 1, 'W' from dual UNION ALL
5 select 2, 'R' from dual
6 )
7 select
8 id,
9 DECODE(
10 MIN(
11 DECODE(status,'S',1,'W',2,'R',3)
12 ),
13 1,'S',2,'W',3,'R') "status"
14 from xx
15 group by id;
ID s
---------- -
1 S
2 R
Here, logic is quite simple.
Do a DECODE for setting the 'Priority', then find the MIN (i.e. one with Higher Priority) value and again DECODE it back to get its 'Status'

Answer 7

Using MOD() example with added values:
SELECT id, val, distinct_val
FROM
(
SELECT id, val
, ROW_NUMBER() OVER (ORDER BY id) row_seq
, MOD(ROW_NUMBER() OVER (ORDER BY id), 2) even_row
, (CASE WHEN id = MOD(ROW_NUMBER() OVER (ORDER BY id), 2) THEN NULL ELSE val END) distinct_val
FROM
(
SELECT 1 id, 'R' val FROM dual
UNION
SELECT 1 id, 'S' val FROM dual
UNION
SELECT 1 id, 'W' val FROM dual
UNION
SELECT 2 id, 'R' val FROM dual
UNION -- comment below for orig data
SELECT 3 id, 'K' val FROM dual
UNION
SELECT 4 id, 'G' val FROM dual
UNION
SELECT 1 id, 'W' val FROM dual
))
WHERE distinct_val IS NOT NULL
/
ID VAL DISTINCT_VAL
--------------------------
1 S S
2 R R
3 K K
4 G G