T-SQL Query | [ The Gap Puzzle – III ]

Puzzle Description

1. We have a table called FindGaps with a single column col1.
2. If we have gap of more than 2 then we will conside that as a GAP.
3. We have to find out the gaps between these numbers in two columns like when the Gap starts and when the gap ends.
4. Please check out the sample input and expected output for details

Sample Input

Col1
1
3
4
5
6
7
9
11
15
17

Expected Output

RangeStart	RangeEnd
1	11
15	17

Rules/Restrictions

• The solution should be should use “SELECT” statement or “CTE”.
• Add your solution(s) in the comments section or send you solution(s) to pawankkmr@gmail.com

Script

Use the below script to generate the source table and fill them up with the sample data.

--

CREATE TABLE FindGaps
(
	Col1 INT
)
GO

INSERT INTO FindGaps(Col1)
VALUES (1),(3),(4),(5),(6),(7),(9),(11),(15),(17)

CREATE CLUSTERED INDEX Ix_Gaps ON FindGaps(Col1)

--

Update June 16 | Solution1 – Pawan Kumar Khowal

--

;WITH CTE
AS
(
SELECT
	 COl1
	,CASE WHEN COl1 - lag(col1) OVER (ORDER BY COl1) <= 2 THEN 0 ELSE 1 END rnk
FROM FindGaps
)
,CTE2 AS
(
	SELECT COl1,SUM(rnk) OVER (ORDER BY Col1 rows unbounded preceding) grouper
	FROM CTE
)
SELECT MIN(col1) RangeStart , MAX(col1) RangeEnd FROM CTE2
GROUP BY grouper

--

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Pawan Kumar Khowal