Final sql statement to generate secondary tide events.
Script to verify select statement used in trigger.
Added document describing how subtype-supertype relationships can be implemented in a sql database.
Removed embreyonic sub-supertype relationship description.
Removed test sql script file.
Added tide data for Nelson 2011-2012.
Replaced stored secondary_tide_events table with a view so that they are calculated as needed.
Removed trigger that generated secondary_tide_events when creating a trip.
Created view trip_tide_events, showing all tide_events during all trips.