low performance

Hi, I'm a new member here and I'm a beginner in SQL query.
Recently, I've built a web application using ASP.NET 2.0 and SQL server 2005 express and in my client, they use SQL server 2005 (I don't know which version but I'm sure it's not express edition). I've deployed my application a month ago and now they complain me about the performance degradation. Since I know just a basic SQL query knowledge and I do know the low performance cause might be the huge data entered there, I would like to know what would be the other cause of the low performance problem. Anyone can help me? And do you have any suggestion on how to fix the poor performance?
FYI: All the tables already in 3NF and I broke the rule of 3NF a little (I make a calculated column in some tables because I need it for complicated process). Almost query I built is in stored procedure and no dynamic SQL in stored procedure at all.

First of all, welcome to the forums.
I have a couple of points to raise:

• Generally when customers complain of low performance, it applies to low respond time of the application and not necessarily low performance from SQL Server point of view. So you may have to ask from them on what exactly they mean as performance degradation.
• As they say it is degraded from where it was a month ago, it could be due to the data load. Please check for the following

• Do you have indexes on columns used by WHERE Clause in your SQL code.
• Are you loading only the rows and columns needed. Most common mistake will be SELECT *
• Are you managing a good balance between round trips (the number of times you have database calls) and the data you are loading.

• Please refer the performance tips from this site. They are very useful to improve performance. http://www.sql-server-performance.com/tips/all_main.aspx
• You can also run profiler to get the worst offenders and resolve them Read this article:

http://www.simple-talk.com/sql/perf...es-of-poor-performance-in-sql-server,-part-1/
Hope this helps!

Thanks Preethi for the answer. I will try to do something about this low performance. I've read the article you pointed to. It seems some of problem explained there.
Thanks again. Regards. Roby

You are welcome. Happy to Help

Does your application frequently update fields that are indexed? That may be contributing to slow response times as well.