SQL Prompt Syntax - Parent Account Issue

 Hello, 

Does anyone have a list of the appropriate syntax for SQL in the report prompts.  We are having a problem with our reports excluding the information from a Parent Account when prompted on Parent Account since the Parent Account itself has a null value in that field since nobody is above them in the heirarchy.  Our reports all start with identifying the Parent since they are the contract holder so the fact that they are being excluded is quite a business issue. I am thinking we can write a SQL statement that would include this but I do not know