JSON_AGG
AggregateAggregates values into a JSON array (PostgreSQL).
Syntax
JSON_AGG(expression)
Example
SELECT department,
JSON_AGG(json_build_object('name', name, 'salary', salary)) as staff
FROM employees
GROUP BY department;About SQL JSON_AGG
The JSON_AGG keyword belongs to the Aggregate category of SQL statements. Aggregates values into a JSON array (PostgreSQL). 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 JSON_AGG 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 JSON_AGG: 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.