https://github.com/metabase/metabase/issues/3324 Hi again. have a look at that github issue, for me it works when I don´t give an alias to my tables.
So rather than
FROM db_summary_syn a
LEFT join users b ON a.codfis=b.codfis
LEFT join db_companies c ON a.idcompany=c.id
you should write:
FROM db_summary_syn
LEFT join users ON db_summary.codfis=users.codfis
LEFT join db_companies ON db_summary.idcompany=db_companies.id
its worth a try 