Thanks for clarification. Sorry that I do not think I understand circular dependency and compsite key very well.
Also can you help me to read the circular dependency error message? I mean How to find the circle from the error message of "Circular Dependency". Here is the error message: sqlalchemy.exc.CircularDependencyError: Circular dependency detected [(DataValues, Groups), (DataValues, DerivedFrom), (Sites, TexasStream), (Sites, DataValues), (Sites, ReservoirRatingCurve), (Sites, Reservoir), (TexasStream, HydrologicUnit), (TexasStream, MajorWaterRight), (TexasStream, Reservoir), (Reservoir, MajorWaterRight), (Reservoir, ReservoirRatingCurve), (Reservoir, StorageInformation), (MajorWaterRight, Reservoir), (HydrologicUnit, Sites)][] Thanks a lot... -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
