MySQL
1. Jar is available here: https://dev.mysql.com/downloads/connector/j/
Choose the Platform Independent option.
Put the jar in the additional libraries folder.
2. Add jSQL library and a reference to the jar (change version as needed):
B4X:
#AdditionalJar: mysql-connector-j-9.4.0
3. Driver + url:
B4X:
sql.Initialize2("com.mysql.cj.jdbc.Driver", "jdbc:mysql://localhost/database_here", Username, Password)
MariaDB
1. Jar: https://mariadb.com/downloads/connectors/connectors-data-access/java8-connector/ (Java 8+ connector)
2.
B4X:
#AdditionalJar: mariadb-java-client-3.5.5
B4X:
sql.Initialize2("org.mariadb.jdbc.Driver", "jdbc:mariadb://localhost/database_here", Username, Password)