Group close numbers

Question

I have a table with 2 columns of integers. The first column represents start index and the second column represents end index.

START END
1     8
9     13
14    2         


        

Answer 1

You could use a number table to solve this problem. Basically, you first expand the ranges, then combine subsequent items in groups.

Here's one implementation:

WITH data (START, [END]) AS (
  SELECT  1,  8 UNION ALL
  SELECT  9, 13 UNION ALL
  SELECT 14, 20 UNION ALL
  SELECT 20, 25 UNION ALL
  SELECT 30, 42 UNION ALL
  SELECT 42, 49 UNION ALL
  SELECT 60, 67
),
expanded AS (
  SELECT DISTINCT
    N = d.START + v.number
  FROM data d
    INNER JOIN master..spt_values v ON v.number BETWEEN 0 AND d.[END] - d.START
  WHERE v.type = 'P'
),
marked AS (
  SELECT
    N,
    SeqID = N - ROW_NUMBER() OVER (ORDER BY N)
  FROM expanded
)
SELECT
  START = MIN(N),
  [END] = MAX(N)
FROM marked
GROUP BY SeqID

This solution uses master..spt_values as a number table, for expanding the initial ranges. But if (all or some of) those ranges may span more than 2048 (subsequent) values, then you should define and use your own number table.