T-SQL Query | [ The Gap Puzzle – II ]

Puzzle Description

1. We have a table called FindGaps with a single column col1.
2. We have to find out the gaps between these numbers in two columns like when the Gap starts and when the gap ends.
3. 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

 GapStart GapEnd 2 2 8 8 10 10 12 14 16 16

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
,COl1 - ROW_NUMBER() OVER (ORDER BY COl1) rnk
FROM FindGaps
)
,CTE1 AS
(
SELECT MIN(Col1) - 1 GStart, MAX(col1) + 1 Gend, ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) rnks FROM CTE
Group By Rnk
)
SELECT CASE WHEN a.GStart >= b.Gend THEN b.Gend ELSE a.GStart END GapStart,
CASE WHEN a.GStart >= b.Gend THEN a.GStart ELSE b.Gend END GapEnd
FROM CTE1 a INNER JOIN CTE1 b ON a.rnks-1 = b.rnks

--

```

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Pawan Kumar Khowal