Display format for data in a relational database. The columns resp. database fields of the database tables of an ABAP-based SAP system are defined in the ABAP Dictionary. Each database table has an unique primary index and can posess additional secondary indexes. Between individual database tables, foreign key dependencies can exist. The definition of a database table is in general specified as a transparent table in the database of the SAP-system. Besides transparent tables there are also SAP-specific definitions as cluster-tables and pool-tables. All database tables defined in the ABAP Dictionary can be referenced as data type (just as flat structures and you can access them with Open SQL .