SQL is a language used to create, read, update, and manage data in relational databases.
A language for asking data questions
SQL can select rows, combine tables, group results, and sort answers. It can also define tables and change records, which is why it sits at the center of many business systems.
Queries are executable plans
A database may choose an index, join order, or scan to answer the same SQL statement. Good SQL expresses the desired result clearly while indexes and query plans help it run efficiently.