It is sometimes necessary to have a variable which is not used. These unused variables should have distinctive names, to make it clear to readers of the code that they are deliberately not used. The most common conventions for indicating this are to name the variable _ or to start the name of the variable with unused or _unused.

The query accepts the following names for variables that are intended to be unused:

• Any name consisting entirely of underscores.
• Any name containing unused.
• The names dummy or empty.
• Any "special" name of the form __xxx__.