What is meant by Data-Definition Language and Data-Manipulation Language with respect to Database Management System?
A database system provides a data definition language to specify the database schema and a data manipulation language to express database queries and updates. Actually, the data definition and data manipulation languages are not two separate languages; instead they simply form parts of a single database language, such as the widely used SQL language. Data-Definition Language We specify a database schema by a set of definitions expressed by a special language called a data-definition language (DDL). For instance, the following statement in the SQL language defines the account table: create table account (account-number char(10), balance integer); Execution of the above DDL statement creates the account table. In addition, it updates a special set of tables called the data dictionary or data directory. A data dictionary contains metadata, that is, data about data. The schema of a table is an example of metadata. A database system consults the data dictionary before reading or modifying a
