Posted by Erland Sommarskog on 01/05/07 23:10

Mintyman (mintyman@ntlworld.com) writes:
> I totally agree with not being spoon fed! I'm sorry I came across as
> wanting to be. I'll try and work out what your script is doing :o)

There is one thing I should have pointed out. In my query there was this
part:

(SELECT a.OrderID, a.ProductID,
rowno = (SELECT COUNT(*)
FROM [Order Details] b
WHERE b.OrderID = a.OrderID
AND b.ProductID <= a.ProductID)
FROM [Order Details] a) AS OD

That is a *derived table*. A derived table is logically a temp table in
the query so to speak, but not materialised, and the actually computation
order can be different as long as the result is the same. Derived tables
is an enormously powerful tool to build complex queries with, and saves
you from using real temp tables.


--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se

Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx

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