As a convention, on RDBMS brands that support sequences
(e.g. Oracle, PostgreSQL, DB2), this method forms the name of a sequence
from the arguments and returns the last id generated by that sequence.
On RDBMS brands that support IDENTITY/AUTOINCREMENT columns, this method
returns the last value generated for such a column, and the table name
argument is disregarded.
On RDBMS brands that don't support sequences, $tableName and $primaryKey
are ignored.