Oracle SQL Grouping In Ranges - sql

Question

I am looking for ideas on how to group numbers into low and high ranges in Oracle SQL. I looking to to avoid cursors...any ideas welcome
Example input
ID
LOW
HIGH
A
0
2
A
2
3
A
3
5
A
9
11
A
11
13
A
13
15
B
0
1
B
1
4
B
7
9
B
11
12
B
12
17
B
17
18
Which would result in the following grouping into ranges
ID
LOW
HIGH
A
0
5
A
9
15
B
0
4
B
7
9
B
11
18

Answer 1

This is a Gaps & Islands problem. You can use the traditional solution.
For example:
select max(id) as id, min(low) as low, max(high) as high
from (
select x.*, sum(i) over(order by id, low) as g
from (
select t.*,
case when low = lag(high) over(partition by id order by low)
and id = lag(id) over(partition by id order by low)
then 0 else 1 end as i
from t
) x
) y
group by g
Result:
ID LOW HIGH
--- ---- ----
A 0 5
A 9 15
B 0 4
B 7 9
B 11 18
See running example at db<>fiddle.

Answer 2

From Oracle 12, you should use MATCH_RECOGNIZE for row-by-row pattern matching:
SELECT *
FROM table_name
MATCH_RECOGNIZE(
PARTITION BY id
ORDER BY low, high
MEASURES
FIRST(low) AS low,
MAX(high) AS high
PATTERN (overlapping* last_row)
DEFINE
overlapping AS NEXT(low) <= MAX(high)
)
Which, for the sample data:
CREATE TABLE table_name (id, low, high) AS
SELECT 'A', 0, 2 FROM DUAL UNION ALL
SELECT 'A', 2, 3 FROM DUAL UNION ALL
SELECT 'A', 3, 5 FROM DUAL UNION ALL
SELECT 'A', 9, 11 FROM DUAL UNION ALL
SELECT 'A', 11, 13 FROM DUAL UNION ALL
SELECT 'A', 13, 15 FROM DUAL UNION ALL
SELECT 'B', 0, 1 FROM DUAL UNION ALL
SELECT 'B', 1, 4 FROM DUAL UNION ALL
SELECT 'B', 7, 9 FROM DUAL UNION ALL
SELECT 'B', 11, 12 FROM DUAL UNION ALL
SELECT 'B', 12, 17 FROM DUAL UNION ALL
SELECT 'B', 17, 18 FROM DUAL UNION ALL
SELECT 'C', 0, 10 FROM DUAL UNION ALL
SELECT 'C', 1, 3 FROM DUAL UNION ALL
SELECT 'C', 5, 8 FROM DUAL UNION ALL
SELECT 'C', 9, 15 FROM DUAL UNION ALL
SELECT 'C', 10, 14 FROM DUAL UNION ALL
SELECT 'C', 11, 13 FROM DUAL;
Outputs:
ID
LOW
HIGH
A
0
5
A
9
15
B
0
4
B
7
9
B
11
18
C
0
15
fiddle