vegbien.sql: Split taxondetermination UNIQUE CONSTRAINT into one constraint for each main key (taxonoccurrence_id, specimen_id, individualplant_id) to deal with Postgres treating a row with NULL in any of those columns as distinct. Added CHECK constraint to require one of taxonoccurrence_id, specimen_id, individualplant_id to be NOT NULL.
vegbien.sql: Split taxondetermination UNIQUE CONSTRAINT into one constraint for each main key (taxonoccurrence_id, specimen_id, individualplant_id) to deal with Postgres treating a row with NULL in any of those columns as distinct. Added CHECK constraint to require one of taxonoccurrence_id, specimen_id, individualplant_id to be NOT NULL.