Wednesday, April 25, 2007

Software as a service

Software as a service (SaaS) is a software application delivery model where a software vendor develops a web-native software application and hosts and operates (either independently or through a third-party) the application for use by its customers over the Internet.

Wednesday, April 04, 2007

Jeff Smith: Conditional Joins in SQL Server

Itt van reszletesen, de a lenyeg:

Sometimes, when writing SELECTs, we come across situations in which we we need to write a join containing a condition of some sort. You might think to do this with either a CASE expression or with some OR boolean logic in your JOIN expression. Often, you might encounter syntax errors, performance problems, or results not being returned the way you expect when trying this. There’s a much better way to approach the problem.

Instead of trying to alter a single INNER JOIN’s relation from row to row, instead use multiple LEFT OUTER JOINS in your SELECT, one for each table or condition that you need to consider.

Transact-SQL: ISNULL(), COALESCE()

COALESCE(Transact-SQL): Returns the first nonnull expression among its arguments.

ISNULL(Transact-SQL): Replaces NULL with the specified replacement value.