Differance between DDL and SDL?
DDL and SDL - The data definition language (DDL) is used through DBA and database designers to describe internal schema, conceptual schema, and mappings between these two. In a few DBMSs, a clear separation is maintained among conceptual schema and internal schema. In that case, DDL is used to exact the conceptual schema only. The other language, storage definition language (SDL) is used to specify the internal schema. The mappings among the two schemas may be specified in either one of these languages.