PostgreSQL and MySQL are leading open-source relational databases. PostgreSQL offers advanced features like full-text search, JSONB, and custom data types. MySQL prioritizes speed and simplicity for read-heavy workloads. PostgreSQL supports with CTEs, window functions, and recursive queries. MySQL has limited window function support and no recursive CTEs. PostgreSQL's MVCC implementation handles concurrent writes efficiently. MySQL's InnoDB engine provides good performance for most workloads. PostgreSQL supports partial indexes, expression indexes, and GiST indexes. MySQL indexes are simpler but effective for common use cases. PostgreSQL excels at data integrity with CHECK constraints and exclusion constraints. MySQL sacrifices some integrity for performance. PostgreSQL supports materialized views and triggers comprehensively. MySQL introduced materialized views through generated columns. PostgreSQL has better support for GIS and spatial data with PostGIS. MySQL has basic geometric functions. PostgreSQL replication offers streaming, logical, and cascading options. MySQL offers asynchronous and semi-synchronous replication. PostgreSQL is licensed under PostgreSQL License (similar to MIT). MySQL has dual license with GPL and commercial options. Choose PostgreSQL for complex queries and data integrity. Choose MySQL for simplicity and read-heavy workloads.