DISTINCT
QueryRemoves duplicate rows from the result set, returning only unique values.
Syntax
SELECT DISTINCT col FROM table
Example
SELECT DISTINCT category FROM products ORDER BY category;
About SQL DISTINCT
The DISTINCT keyword belongs to the Query category of SQL statements. Removes duplicate rows from the result set, returning only unique values. Understanding this command is essential for any developer working with relational databases like PostgreSQL, MySQL, SQLite, or SQL Server.
SQL (Structured Query Language) is the standard language for managing and querying relational databases. The DISTINCT statement is supported across all major database systems, though specific syntax may vary slightly between PostgreSQL, MySQL, MariaDB, Oracle, SQL Server, and SQLite. Always consult your database's documentation for vendor-specific features and limitations.
Best practices for using DISTINCT: always test queries on a development database before running them in production, use parameterized queries to prevent SQL injection, and leverage EXPLAIN to understand query performance. For complex queries, consider using CTEs (Common Table Expressions) to improve readability and maintainability.