EDIT: Never mind - you actually mentioned this.

A lot of this is over my head... but it is my understanding that at a certain point you are comparing queries that...

• This reply was modified 5 years, 5 months ago by  cranberry.

This is the solution I came up with.  Obviously not ideal SQL, but it works within the limitations of the table structure, runs much faster and is (surprisingly) less onerous...

That is an interesting idea.  I could possibly use a window function to establish the PreReq#:

SELECT [t].[PERSONID]
   ,[t].[EVENT_ID]
   ,[p].[SEQUENCE_NUMBER]
   ,[p].[OPEN_PARENS]
   ,[p].[PREREQ_EVENT_ID]
  ...