As explained in Section 1.5, for supporting variety of users, a DBMS must provide appropriate languages and interfaces for each category of users to express database queries and updates. Once the design of database is complete and a DBMS is chosen to implement the database, it is important to first specify the conceptual and internal schemas for the database and any mappings between the two. Following languages are used to specify database schemas:
Data definition language (DDL)
Storage definition language (SDL)
View definition language (VDL)
Data manipulation language (DML)
Fourth-generation language (4GL)
In practice, the data definition and data manipulation languages are not two separate languages. Instead they simply ...