How to find N Consecutive records in a table using SQL

Question

I have the following Table definition with sample data. In the following table, Customer Product & Date are key fields

Table One
Customer   Product    Date         SALE
   X          A       01/01/2010    YES
   X          A       02/01/2010    YES
   X          A       03/01/2010    NO
   X          A       04/01/2010    NO
   X          A       05/01/2010    YES
   X          A       06/01/2010    NO
   X          A       07/01/2010    NO
   X          A       08/01/2010    NO
   X          A       09/01/2010    YES
   X          A       10/01/2010    YES
   X          A       11/01/2010    NO
   X          A       12/01/2010    YES

In the above table, I need to find the N or > N consecutive records where there was no sale, Sale value was 'NO' For example, if N is 2, the the result set would return the following

     Customer   Product    Date         SALE
       X          A       03/01/2010    NO
       X          A       04/01/2010    NO
       X          A       06/01/2010    NO
       X          A       07/01/2010    NO
       X          A       08/01/2010    NO

Can someone help me with a SQL query to get the desired results. I am using SQL Server 2005. I started playing using ROW_NUMBER() AND PARTITION clauses but no luck. Thanks for any help

Answer 1

You need to match your table against itself, as if there where 2 tables. So you use two aliases, o1 and o2 to refer to your table:

SELECT DISTINCT o1.customer, o1.product, o1.datum, o1.sale
  FROM one o1, one o2
  WHERE (o1.datum = o2.datum-1 OR o1.datum = o2.datum +1)
  AND o1.sale = 'NO' 
  AND o2.sale = 'NO'; 
 customer | product |   datum    | sale 
----------+---------+------------+------
 X        | A       | 2010-01-03 | NO
 X        | A       | 2010-01-04 | NO
 X        | A       | 2010-01-06 | NO
 X        | A       | 2010-01-07 | NO
 X        | A       | 2010-01-08 | NO

Note that I performed the query on an postgresql database - maybe the syntax differs on ms-sql-server, maybe at the alias 'FROM one AS o1' perhaps, and maybe you cannot add/substract in that way.