SQL means "Structured Query Language", and is used to *search* through
existing relational database management systems (RDBMS).
In 2020, the most used RDBMS options[1] are (most-lowest):
1. Oracle DB
2. MySQL
3. Microsoft SQL Server
4. PostgreSQL
5. SQLite
Google trends (2020) ranked the same systems in the order:
1. MySQL
2. Microsoft SQL Server
3. PostgreSQL
4. Oracle DB
5. SQLite
MySQL, PostgreSQL and SQLite are Open Source and 'Free'.
- MySQL's shell handles JavaScript, Python and formerly Perl.
You can find drivers for the mysql connectors in most languages.
- PostgreSQL's interface layer is open to most languages. The
psql shell interpets PL/pgSQL, a custom language for the DBMS.
- SQLite has a single custom shell language, but supports bindings
in most well known programming languages. SQLite is installed
automatically on some Unix/Linux distributions.
References:
[1] https://db-engines.com/en/ranking