SQL (Structured Query Language) is a domain-specific language used in programming and designed for managing and manipulating data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS).
Here are some key points about SQL:
Standardized Language: SQL is an ANSI (American National Standards Institute) and ISO (International Organization for Standardization) standardized language, which means it follows a defined set of rules and syntax.
Data Definition and Manipulation: SQL allows users to define, manipulate, and control data stored in a relational database management system. It includes commands for creating and modifying database structures (such as tables, indexes, and views) as well as manipulating data (such as inserting, updating, deleting, and querying).
Declarative Language: SQL is a declarative language, which means users specify what they want to achieve rather than how to achieve it. Users write SQL queries to describe the desired results, and the database management system determines the most efficient way to execute the query.
Query Language: SQL is primarily used as a query language to retrieve information from databases. Users can write SELECT statements to query data based on specified criteria.
Data Integrity and Security: SQL provides mechanisms for ensuring data integrity (such as constraints and referential integrity) and enforcing security (such as user authentication, authorization, and access controls).
Transaction Control: SQL supports transaction control commands that allow users to manage transactions, ensuring data consistency and integrity in multi-user environments.
Support for Procedural Constructs: Some versions of SQL include procedural extensions, such as stored procedures, functions, triggers, and control-flow statements, allowing users to define and execute procedural logic within the database.
SQL is widely used across various industries and is essential for working with relational databases. It's the backbone of many applications and systems that rely on structured data storage and retrieval. Examples of popular relational database management systems that support SQL include MySQL, PostgreSQL, Oracle Database, Microsoft SQL Server, SQLite, and many others.