1. SQL allows users to access data in relational database management systems

2. There are three groups of SQL commands viz., DDL, DML and DCL.

3. The Data Definition Language (DDL) part of SQL permits database tables to be created or deleted.

4. SQL language also includes syntax to update, insert, and delete records. These query and update commands together form the Data Manipulation Language (DML) part of SQL.

5. The SQL Data Control Language (DCL) provides security for your database. The DCL consists of the GRANT, REVOKE, COMMIT, and ROLLBACK statements.

6. Constraints are a way to limit the kind of data that can be stored in a table.

7. Relational databases like SQL Server use indexes to find data quickly when a query is processed.