WHERE
FilteringFilters rows based on a specified condition. Only rows meeting the condition are included in results.
Syntax
SELECT columns FROM table WHERE condition
Example
SELECT * FROM products WHERE price > 50 AND category = 'electronics';
About SQL WHERE
The WHERE keyword belongs to the Filtering category of SQL statements. Filters rows based on a specified condition. Only rows meeting the condition are included in results. 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 WHERE 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 WHERE: 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.