Be very careful when using queries with large result sets as they can cause problems.
For example:

• Notifications to a large amount of recipients will cause the mail server to send this large amount of emails for each scheduled notification
  
• If the execution time of the used queries is greater than the notification check period defined in Schedule tab, the execution of the notification task will NOT finish in time

When writing queries please make them as specific as possible to prevent your queries from having a negative effect on the performance of ConnectionsExpert. For instance by already filtering in the query itself (using "WHERE" statements) instead of in the notification settings or by limiting the number of columns to return only those used in your notification settings.