The Database Definition Language(DDL) is a database language. It uses SQL statements to define all attributes and properties of a database management system( DBMS) and to create and manage database objects within a database.
The DDL command Create has a predefined syntax. It is used to build new database tables. The Alter command can be used to modify existing tables. Additional columns can be inserted, existing columns can be deleted and the data type in the columns can be changed. And with the Drop command a table or an index can be deleted.