**query functions** are dynamic functions which connect
to a database, execute queries in it and transform data.
Actually it is a decorator for execute function.
execute has 5 arguments. The first argument is an
instance of the sqliter class and the second is
the database name. The call to a query function is
executed like a method call to the sqliter object
through the $ operator. The function name must
have the following pattern: query_. This call returns an execute
function with the first 2 argument already set. The first
parameter is the sqliter object on which the
$ operator have been called and the second
argument is extracted from the query function name, the
name after the preffix query_.