Longest gap between test matches in Sachin's career - sql-server

Question

I am new to SQL server and was practising using Sachin's batting stats (Cricket) I found here. (Sachin Batting Statistics). I wanted to find the longest gap between two test matches in Sachin's career. So basically have to filter it based on Test matches and find the max difference in the Start_DateAscending column? Hope that made some sense. Sample table added if link doesn't make sense
EDIT: I created a sample table with different dates. the column is named DateValues. Now, I want to find the code for maximum difference between any two successive rows in the DateValue column. For example, in this case the answer is 2 years and 17 days between December 09, 1989 and December 26, 1991
IF OBJECT_ID('TempDB..#mytable','U') IS NOT NULL
DROP TABLE #mytable
CREATE TABLE #mytable
(
ID INT IDENTITY(1,1) PRIMARY KEY CLUSTERED,
DateValue DATETIME
)
SET DATEFORMAT DMY
SET IDENTITY_INSERT #mytable ON
INSERT INTO #mytable
(ID, DateValue)
SELECT '11', 'Nov 15 1989 12:00AM' UNION ALL
SELECT '59', 'Nov 23 1989 12:00AM' UNION ALL
SELECT '37', 'Dec 09 1989 12:00AM' UNION ALL
SELECT '44', 'Dec 26 1991 12:00AM' UNION ALL
SELECT '55', 'May 31 1993 12:00AM' UNION ALL
SELECT '60', 'May 15 1995 12:00AM' UNION ALL
SELECT '57', 'Jan 12 1996 12:00AM' UNION ALL
SELECT '43', 'Jan 19 1996 12:00AM' UNION ALL
SELECT '49', 'Jan 31 1996 12:00AM' UNION ALL
SELECT '18', 'Oct 17 1997 12:00AM'
Here's a solution I found on this website, the answer I obtained was 1900-01-01!
SELECT MAX(#mytable.DateValue-h.DateValue) as maxDiff
FROM #mytable
LEFT JOIN #mytable h
ON h.ID=[dbo].#mytable.ID AND #mytable.DateValue>=h.DateValue
WHERE h.DateValue IS NOT NULL

Answer 1

If you're using SQL Server 2012 or above, this SQL will return the biggest gap in days between two tests:
select max(datediff(day, a.TestDate, a.NextTest)) as BiggestGap
from (
select DateValue as TestDate, lead(DateValue) over (order by DateValue) as NextTest
from #mytable m
) a
The first thing this query does (inside the parenthesis) is gets a table that lists all test matches and the date of the next test match. That's what the innermost query provides: It selects all test dates and, using the lead function, the date of the match straight after that test.
The data from that parenthesised select (including ID) looks like this:
ID TestDate NextTest
----------- ----------------------- -----------------------
11 1989-11-15 00:00:00.000 1989-11-23 00:00:00.000
59 1989-11-23 00:00:00.000 1989-12-09 00:00:00.000
37 1989-12-09 00:00:00.000 1991-12-26 00:00:00.000
44 1991-12-26 00:00:00.000 1993-05-31 00:00:00.000
55 1993-05-31 00:00:00.000 1995-05-15 00:00:00.000
60 1995-05-15 00:00:00.000 1996-01-12 00:00:00.000
57 1996-01-12 00:00:00.000 1996-01-19 00:00:00.000
43 1996-01-19 00:00:00.000 1996-01-31 00:00:00.000
49 1996-01-31 00:00:00.000 1997-10-17 00:00:00.000
18 1997-10-17 00:00:00.000 NULL
After that (outside the parenthesis), it's simply a case of finding the row with the biggest difference between dates. In SQL Server, it's best to use the datediff function to get the difference between two dates instead of using mathematical operators such as - in the example you saw, so we use that to get the difference in days between each row. max is used to get the largest of those, thus returning the biggest gap between two matches.
Using the example SQL data provided, the biggest gap is 747 days (approximately 2 years 17 days).