This probably needs verification, so run at your own risk!

The SQL statement to delete would be: DELETE from person where name = '...'

person is the table of users.

name = '...' is the condition for the row that is to be deleted.

You can also modify the condition to, for example, delete a user using the id instead of their name (username).

Here’s a link to the “schema” of the person table as generated by the backend code.