8  DDL

Data Definition Language (DDL)

8.1 DDL

Data Definition Language (DDL)

Data Definition Language (DDL) supports database schemas and descriptions. DDL commands manages the structure of database objects.

  • Common DDL SQL commands include: CREATE, ALTER, DROP, TRUNCATE

  • Data structure: Records, Fields, Tables, Database

  • Prepare the schema for the RDBMS

  • Identify all tables in the database

  • Create table with domains and data types

  • Give each table a primary key

  • Ensure that every table has at least one column in common with one other table

  • Check constraints on columns and tables

  • Prevent anomalies and data redundancies during insertion, deletion, and update operations

  • Check entity, referential and domain integrity

  • Criteria for normalizing the database include the five standard normal forms (1NF to 5NF) and other normalization strategies

  • Check this Wikipedia article on the data normalisation.