# Database Languages

Broadly speaking, there are two categories of database languages:

* Data Manipulation Language (DML)
* Data Definition Language (DDL)

## Data Manipulation Language (DML)

* It is also known as **query language**
* It is used to access and manipulate the data stored in a database
* It has two sub-categories: **procedural** (the user specifies what data is required and how to compute the data) and **declarative**/**non-procedural** (the user specifies what data is required without specifying how to compute the data)
* SQL (Structured Query Language) is the most widely used query language and is non-procedural
* Some common DML commands include **SELECT**, **INSERT**, **UPDATE**, **DELETE**

## Data Definition Language (DDL)

* It is used to define the database schema, the storage structure, integrity constraints and the authorizations on the database content and operations
* The DDL compiler generates a set of tables stored in a **data dictionary**
* The data dictionary contains metadata including the database schema, the storage structure (specified using *data storage and definition language*), integrity constraints (such as domain constraints, referential integrity, assertions etc) and authorization information
* Some common DDL commands include **CREATE**, **ALTER**, **DROP**

SQL is, therefore, both a DML and a DDL.