INTERSECT
SetReturns only rows that appear in both SELECT result sets.
Syntax
SELECT cols FROM t1 INTERSECT SELECT cols FROM t2
Example
SELECT product_id FROM orders_2023 INTERSECT SELECT product_id FROM orders_2024;
About SQL INTERSECT
The INTERSECT keyword belongs to the Set category of SQL statements. Returns only rows that appear in both SELECT result sets. 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 INTERSECT 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 INTERSECT: 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.