SQL as Relational Language

SQL = Structured Query Language is a database sublanguage for querying and modifying relational databases. It was developed by IBM Research in the mid 70's and standardized by ANSI in 1986.

It is the database language of choice for many relational database systems including PostgreSQL, MySQL, Microsoft SQL Server, Oracle, DB2, INGRES and SYBASE.

The Relational Model defines two root languages for accessing a relational database:

Relational Algebra: Relational Algebra is a low-level, operator-oriented language. Creating a query in Relational Algebra involves combining relational operators using algebraic notation.
Relational Calculus: Relational Calculus is a high-level, declarative language. Creating a query in Relational Calculus involves describing what results are desired.

SQL is a version of Relational Calculus.

What can SQL do ?

SQL allows you to access a database
SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert new records in a database
SQL can delete records from a database
SQL can update records in a database

SQL is easy to learn.