How to enable line numbers in Oracle SQL Developer?
Line numbering is a very helpful feature, especially when you need to go to a code line specified in the error message. The feature is disabled by default in Oracle SQL Developer.
To enable the feature, right click in the line gutter (space before the vertical line on the left side) in Worksheet and click on Toggle Line Numbers:
This setting can be also changed in Preferences. Go to Code Editor / Line Gutter tab and check Show Line Numbers:
Another helpful thing may be to enable word wrap-like functionality – see how to break line to the right margin in SQL Developer.