COALESCE

Function

Returns the first non-NULL argument. Useful for providing default values.

Syntax

COALESCE(val1, val2, ..., default)

Example

SELECT name,
       COALESCE(nickname, first_name, 'Unknown') AS display_name
FROM users;

About SQL COALESCE

The COALESCE keyword belongs to the Function category of SQL statements. Returns the first non-NULL argument. Useful for providing default 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 COALESCE 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 COALESCE: 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.

Related SQL Keywords

IS NULLCASE