The following may be one of the cause that your query become slow.

1. May be your SQL Server becomes busy. What I mean is that when your testing it before there are only few users on the server. The number of users connected to the server will affect the performance.

2. May be your SQL Server have more jobs to do. May be your SQL Server is also your domain controller, print server, e-mail server. SQL Server works better if it not installed in the domain controller machine, print server, e-mail server. If this is the case, this will cause an overhead on your system because of the many process need to execute. Try to monitor your server using Network Monitoring tools.

3. May be the there is no enough disk space on your server. Try to check the disk space.


Using cursor is not a good approach of creating query. Cursor need more resources on your PC to execute it. May be you can revise your stored procedure to use query if possible.