PostgreSQL and MySQL are both open source relational databases. They both offer an SQL interface for creating and manipulating data.
The main difference between PostgreSQL and MySQL is the level of compliance with the SQL standard. PostgreSQL is fully compliant with the SQL standard, while MySQL is not. PostgreSQL also offers more advanced features than MySQL, such as stored procedures, triggers, and foreign key constraints.
For example, PostgreSQL supports stored procedures, which allow users to write functions that can be called from within an SQL query. This allows for more complex logic to be implemented within the database, without having to write application-level code. MySQL does not support stored procedures.
Another example is foreign key constraints. PostgreSQL supports foreign key constraints, which allow you to define relationships between tables and ensure that data is consistent across them. MySQL does not support foreign key constraints.