A schema consists of metadata definitions such as tables, views,
    domains, constraints, collating sequences, indexes, storage maps,
    triggers, and the privileges for each of these.

    You name schemas in CREATE SCHEMA or CREATE DATABASE statements.
    You can also use schema names to qualify the names of other
    database elements such as tables, views, and columns.

                                   NOTE

       In syntax diagrams, the schema-name syntax element refers to
       either the qualified or unqualified form of the name given
       to the schema in the CREATE statement. That is, in syntax
       diagrams, the schema-name is always defined as:

  schema-name  =

  --+---------------------------------------------+
    +------> <catalog-name> --------------+->. ---+
    +-> " -> <alias>.<catalog-name> ->" --+       |
    |   +-----------------------------------------+
    |   +--------------> <name-of-schema> ------+->
    +-> " -> <alias>.<name-of-schema> ->" ------+

    By default, each database that you create has only one schema.
    CREATE DATABASE tells how to create a multischema database.
    The alias RDB$DBHANDLE represents the schema when you refer
    to definitions in a single-schema database or definitions in a
    multischema database without multischema naming enabled.

    When you refer to definitions in a multischema database, you must
    follow multischema naming rules unless you disable multischema
    naming. In multischema naming:

    o  You must qualify definition names using the name of the schema
       that contains them. You cannot refer to a table and a view
       or two objects of the same type (such as two tables) with the
       same name unless they belong to different schemas.

    o  You may additionally qualify the names of objects in a
       multischema database with the alias and the catalog name.

       Whenever you qualify the object name with a catalog name,
       you must also specify the schema name, unless you want to use
       the default schema. Remember that the catalog name and alias
       combination or the schema name and alias combination must be
       enclosed within double quotation marks.

    o  If you prefer, you can qualify an object name in a multischema
       database with just an alias, provided you have set the default
       catalog and schema to the ones that you want to contain the
       object. Enclose the alias and object name pair within double
       quotation marks and separate them with a period.

    If you omit the schema name when referring to objects in a
    multischema database, SQL uses a schema with the same name as
    the user identifier of the invoker as the default schema. You can
    use the SET SCHEMA statement to change the default schema.