SQL & PL/SQL

Hi - when I downloaded and started to use the SQL developer tool, once I connected, I could see all of the tables/columns in my connection on the left side of the tool, and I had my query panel, results panel, and SQL history stacked on the right. Suddenly something has changed, and I cannot see the list of tables, etc. in my connection anymore, so I have to rely on memory and SQL history to remember the table and column names. It has to be "hidden" somehow, but view-connections does not help, and trying to click and drag windows doesn't uncover it either.

Any suggestions?

Thanks!