The document provides an overview of SQL and relational databases:
- SQL is a widely used language for database administration, enterprise applications, and data-driven websites. It allows querying and managing data stored in relational databases.
- Relational databases are based on Codd's relational model and store data in tables made up of rows and columns. They support constraints, relationships, and other features to ensure data integrity.
- Common SQL statements include DDL for defining database schema, DML for manipulating data, and DCL for controlling access. Key DML commands are SELECT, INSERT, UPDATE, DELETE. SELECT can include WHERE clauses with operators like LIKE, IN, BETWEEN to filter results.