> For the complete documentation index, see [llms.txt](https://vikram-bajaj.gitbook.io/cs-gy-6083-principles-of-database-systems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://vikram-bajaj.gitbook.io/cs-gy-6083-principles-of-database-systems/sql/introduction-to-sql.md).

# Introduction to SQL

SQL is a data definition language that allows the specification of not only a set of relations but also information about each relation, including:

* The schema for each relation
* The domain of values associated with each attribute
* Integrity constraints
* The set of indices to be maintained for each relation
* Security and authorization information for each relation
* The physical storage structure of each relation on disk