The out of the box behaviour of SQL Developer is that SQL worksheets share the same connection.
What does that mean?
If you perform a insert, update or delete in one worksheet without issuing a commit, the result(s) can be viewed in another shared worksheet. This can be illustrated by the following example.
After launching SQL Developer and connecting to a database, I start two new SQL worksheets
The next two screen shots show that for both SQL worksheets that the table t is empty
Next using using the first worksheet, an insert into table t operation is performed. No commit has been issued.
Navigating to the second worksheet and querying the table again and the newly inserted row can be seen.
It is possible to open a SQL Worksheet with a dedicated database connection. In SQL Developer this is called an unshared connection.
From an existing worksheet the keyboard shortcut on Windows is CTL + SHIFT + N. This will only work from a shared worksheet. It is not possible to open a new unshared worksheet from an existing unshared worksheet.
The following screenshots demonstrates how an unshared connection differs from a shared connection.
Two shared SQL Worksheets: hr and hr~1 are started along with and one unshared: hr (Unshared). In the first worksheet I perform an insert operation which has not been committed.
Switching to the second shared worksheet, the uncommitted record is shown after querying the table.
Moving to the unshared connection and querying the table no row is returned.
The unshared worksheet is working as expected as a new session will not see uncommitted records.
Jeff Smith, the Oracle Product manager for SQL Developer has a superb blog where he shares many SQL Developer hints and tips. One of the posts
Opening Unshared Worksheets was the inspiration and source for this post.