[BioSQL-l] Tables without a (composite) primary key

[Peter]

I've recently been looking into some object-relational mappers which
caused me to look more closely at the BioSQL schema.  Many of these
packages require a primary key, but not all can cope with a composite
primary key.  However, some BioSQL tables don't have any primary key
at all.

Several BioSQL tables have composite primary keys, for example the
term_dbxref table has a composite key of (term_id, dbxref_id), and
also an index on dbxref_id as well.

However, some BioSQL tables do not have a primary key, for example:

-- corresponds to the names table of the NCBI taxonomy databaase
CREATE TABLE taxon_name (
       taxon_id		INT(10) UNSIGNED NOT NULL,
       name		VARCHAR(255) BINARY NOT NULL,
       name_class	VARCHAR(32) BINARY NOT NULL,
       UNIQUE (taxon_id,name,name_class)
) TYPE=INNODB;

CREATE INDEX taxnametaxonid ON taxon_name(taxon_id);
CREATE INDEX taxnamename    ON taxon_name(name);

Why don't taxon_name, bioentry_path, term_relationship,
bioentry_qualifier_value, seqfeature_path have a primary key (just a
uniqueness criteria)?

Thanks,

Peter