Requirements for Database server in Drupal

MySQL server, MariaDB server, and Percona Server

Minimum required:

• MySQL Server 5.5.3
• MariaDB Server 5.5.20
• Percona Server 5.5.8 

or higher with InnoDB as the essential storage engine. 

MySQL 8 is supported with Drupal 8.6 or above. 

Drupal itself will by and large work with a default MySQL setup. A more perplexing site will probably require arrangement changes for the DB.

PostgreSQL 

Drupal 8 requires PostgreSQL 9.1.2 or above. 
Drupal 9 requires PostgreSQL 10.0 or above with the pg_trgm expansion. 

Some contributed modules are not as preoccupied with MySQL-explicit code as everybody might want. 

SQLite 

SQLite versions support 3.6.8 or above.

Some contributed modules are not as disconnected from MySQL-explicit code as everybody might want.