The SET SCHEMA schema_name statement sets the schema for the session. If schema is not the same as the current user then all further unqualified object references are treated as if the schema value had been explicitly provided as a qualification.

For example, SET SCHEMA john applies "john." to all unqualified object references. So SELECT * FROM mytab becomes SELECT * FROM from john.mytab.

The current schema_name can be retrieved using: SELECT DBMSINFO('SESSION_SCHEMA')

SET SCHEMA (with no parameters) or SET NOSCHEMA resets schema_name to the current session user.

SET SCHEMA is ignored for all system catalogs.