This topic demonstrates how to collect and spread values from multiple rows under a single column, like those in VAL below
GROUP_KEY VAL ---------- ---------- G4 a G4 b G4 c G4 d G7 a G7 b G7 c G7 d G7 e G7 f G7 g
across multiple columns, rows, and groups like this.
GROUP_KEY COL_0 COL_1 COL_2 ---------- ---------- ---------- ---------- G4 a c d G4 b G7 a d f G7 b e g G7 c
Unlike prior topics in this section, here we have a base table with no PIVOT_KEY column. Values will be distributed evenly from top to bottom, then left to right across an arbitrary number of columns (this is sometimes referred to as "newspaper column" style). Empty cells will be distributed evenly as well.
11g PIVOT Solution
break on group_key duplicates skip 1
select
group_key ,
col_0 ,
col_1 ,
col_2
from
( select
group_key ,
pivot_key ,
row_number() over( partition by group_key, pivot_key order by val )
as row_num ,
val
from
( select
group_key ,
ntile(3) over ( partition by group_key order by val ) - 1
as pivot_key ,
val
from t5
) t5a
) t5b pivot
( max(val)
for pivot_key in
(
0 as col_0 ,
1 as col_1 ,
2 as col_2
)
)
order by group_key, row_num ;
GROUP_KEY COL_0 COL_1 COL_2 ---------- ---------- ---------- ---------- G0 G1 a G2 a b G3 a b c G4 a c d G4 b G5 a c e G5 b d G6 a c e G6 b d f G7 a d f G7 b e g G7 c G8 a d g G8 b e h G8 c f
With two columns instead of three the query would look like this.
select
group_key ,
col_0 ,
col_1
-- this line deleted
from
( select
group_key ,
pivot_key ,
row_number() over( partition by group_key, pivot_key order by val )
as row_num ,
val
from
( select
group_key ,
ntile(2) over ( partition by group_key order by val ) - 1 -- use "2" here
as pivot_key ,
val
from t5
) t5a
) t5b pivot
( max(val)
for pivot_key in
(
0 as col_0 ,
1 as col_1
-- this line deleted
)
)
order by group_key, row_num ;
GROUP_KEY COL_0 COL_1 ---------- ---------- ---------- G0 G1 a G2 a b G3 a c G3 b G4 a c G4 b d G5 a d G5 b e G5 c G6 a d G6 b e G6 c f G7 a e G7 b f G7 c g G7 d G8 a e G8 b f G8 c g G8 d h
The sort order can be controlled by changing the ORDER BY clauses in the analytic function arguments.
select
group_key ,
col_0 ,
col_1 ,
col_2
from
( select
group_key ,
pivot_key ,
row_number() over( partition by group_key, pivot_key ORDER BY VAL DESC)
as row_num ,
val
from
( select
group_key ,
ntile(3) over ( partition by group_key ORDER BY VAL DESC) - 1
as pivot_key ,
val
from t5
) t5a
) t5b pivot
( max(val)
for pivot_key in
(
0 as col_0 ,
1 as col_1 ,
2 as col_2
)
)
order by group_key, row_num ;
GROUP_KEY COL_0 COL_1 COL_2 ---------- ---------- ---------- ---------- G0 G1 a G2 b a G3 c b a G4 d b a G4 c G5 e c a G5 d b G6 f d b G6 e c a G7 g d b G7 f c a G7 e G8 h e b G8 g d a G8 f c
How it Works
The ROW_NUM and PIVOT_KEY values created by the inline views are the key to this solution.
break on pivot_key duplicates skip 1
select
group_key ,
pivot_key ,
row_number() over( partition by group_key, pivot_key order by val )
as row_num ,
val
from
( select
group_key ,
ntile(3) over ( partition by group_key order by val ) - 1
as pivot_key ,
val
from t5
where group_key = 'G8'
) t5a
order by group_key, pivot_key, row_num ;
GROUP_KEY PIVOT_KEY ROW_NUM VAL ---------- ---------- ---------- ---------- G8 0 1 a G8 0 2 b G8 0 3 c G8 1 1 d G8 1 2 e G8 1 3 f G8 2 1 g G8 2 2 h
Once the PIVOT_KEY and ROW_NUM columns have been created, VAL values are simply distributed and collapsed using the PIVOT clause the same way they were in the Transposing M:1 topic.
Earlier Versions
For those who are not working with Oracle 11g the following query works in Oracle versions from 8i onward.
break on group_key duplicates skip 1
select
group_key ,
max( decode( pivot_key, 0, val, null ) ) col_0 ,
max( decode( pivot_key, 1, val, null ) ) col_1 ,
max( decode( pivot_key, 2, val, null ) ) col_2
from
( select
group_key ,
pivot_key ,
row_number() over( partition by group_key, pivot_key order by val )
as row_num ,
val
from
( select
group_key ,
ntile(3) over ( partition by group_key order by val ) - 1
as pivot_key ,
val
from t5
) t5a
) t5b
group by group_key, row_num
order by group_key, row_num ;
GROUP_KEY COL_0 COL_1 COL_2 ---------- ---------- ---------- ---------- G0 G1 a G2 a b G3 a b c G4 a c d G4 b G5 a c e G5 b d G6 a c e G6 b d f G7 a d f G7 b e g G7 c G8 a d g G8 b e h G8 c f