How to enable underscore as word character.
Toad for Oracle 10.1 and lower:
1. Go to View | TOAD Options.
2. On the left panel, click on Editor | Behavior.
3. On the right panel, check "Treat underscore as a word character."
4. Click on "Apply" and "OK."
Toad for Oracle 10.5 and higher:
1. Go to View | TOAD Options.
2. On the left panel, click on Editor | Behavior.
3. On the right panel, under "Additional word characters:" ensure that you have "_" in the box.
4. Click on "Apply" and "OK."