1  Default_Database
   SQL allows you to specify an alias that declares the database as
   the default database. Specifying a default database means that
   subsequent statements during the database attachment that refer
   to the default database need not use an alias.

   In the SQL module language, the alias specified in the module
   header is the one that designates the default database. In
   precompiled SQL programs and in interactive SQL, the special
   alias RDB$DBHANDLE designates the default database. In all
   environments, omitting an explicit alias is the same as
   specifying the alias that designates the default database.

   Select More_Information to continue.
 

2  More_Information
   If you do not declare any alias or attach to any database, SQL
   declares the database specified in the logical name SQL$DATABASE
   or configuration parameter SQL_DATABASE as the default database,
   using the FOR FILENAME clause.

   If you declare a database specifying an alias other than the
   one that declares the default database, you must use that alias
   to qualify names of any database elements to which you refer in
   SQL statements. If you omit the alias, SQL assumes the table or
   view must be part of the default database. If there is no default
   database and you omit the alias, SQL generates an error.