There are 5 types

1.data definition type

2.data manipulation

3.data control

4.transaction control

5.data query

SQL is Structured Query Language is a database computer language designed for managing data in relational database management systems (RDBMS).

PostgreSQL is an object-relational database management system (ORDBMS).It is released under a BSD-style license and is thus free software. As with many other open-source programs, PostgreSQL is not controlled by any single company, but has a global community of developers and companies to develop it.

SQLite is an ACID-compliant embedded relational database management system contained in a relatively small (~225 KB) C programming library. The source code for SQLite is in the public domain.

MySQL is a relational database management system (RDBMS) which has more than 6 million installations. MySQL stands for "My Structured Query Language". The program runs as a server providing multi-user access to a number of databases.