Question

I have a database table with the following structure –

Week_End      Sales
2009-11-01    43223.43
2009-11-08     4324.23
2009-11-15    64343.23
...

Week_End is a datetime column, and the date increments by 7 days with each new entry.

What I want is a SQL statement that will identify if there is a week missing in the sequence. So, if the table contained the following data –

Week_End      Sales
2009-11-01    43223.43
2009-11-08     4324.23
2009-11-22    64343.73    
...

The query would return 2009-11-15.

Is this possible? I am using SQL Server 2008, btw.

Answer 1

You’ve already accepted an answer so I guess you don’t need this, but I was almost finished with it anyway and it has one advantage that the selected solution doesn’t have: it doesn’t require updating every year. Here it is:

SELECT T1.*
FROM Table1 T1
LEFT JOIN Table1 T2
ON T2.Week_End = DATEADD(week, 1, T1.Week_End)
WHERE T2.Week_End IS NULL
AND T1.Week_End <> (SELECT MAX(Week_End) FROM Table1)

It is based on Andemar’s solution, but handles the changing year too, and doesn’t require the existence of the Sales column.