What relational database management systems have you worked with?

In my experience with relational databases, I have used the following DBMS:

• MySQL — frequently used for web applications, well-versed in writing queries, optimization, and index tuning.
• PostgreSQL — used for projects requiring advanced features such as working with JSON, full-text search.
• Oracle Database — had experience working on enterprise projects that required high reliability and scalability.

Each of these systems has its own features, but the general principles of working with SQL queries and transactions are similar.