A left join won't necessarily show the combined rows in the result. I'm thinking your SQL statement is wrong, but I'm not sure exactly what you are trying to achieve, so I can't comment on how to improve it.
Maybe try displaying the final SQL statement with:
Than you can cut and paste that into phpMyAdmin and see the full results and try to figure out what query returns the actual results you expect or need. I could help with this in a premier support ticket, but I'd need to have a conversation with you to figure out what you are trying to do and see it in context to figure out what the right SQL statement is.