Luca Pireddu <luca(at)cs(dot)ualberta(dot)ca> writes:
> So, am I wrong in expecting each strain record to appear only once in the
> result set? Or is there something wrong with PostgreSQL?
Could we see a self-contained example (table definitions and sample data
as a SQL script)? I don't really have time to reverse-engineer a test
case from your description ...
regards, tom lane