1. SQL has become the standard relational database language. It has several parts:

• Data definition language (DDL) - provides commands to
  - Define relation schemes.
  - Delete relations.
  - Create indices.
  - Modify schemes.
• Interactive data manipulation language (DML) - a query language based on both relational algebra and tuple relational calculus, plus commands to insert, delete and modify tuples.
• Embedded data manipulation language - for use within programming languages like C, PL/1, Cobol,
  Pascal, etc.
• View Definition - commands for de ning views.
• Authorization - specifying access rights to relations and views.
• Integrity - a limited form of integrity checking.
• Transaction control - specifying beginning and end of transactions.

We will only look at basic DDL, the DML and views. Integrity features will be covered in Chapter 5.