Jeongeun, just adding to what Polina said, so those are the only available Persistence Provider DBs currently supported. However, since ThingWorx allows you connect to some other RDBMS using Relational Databases Connectors via JDBC for RDBMs like Oracle, IBM DB2, MySQL, MS SQL etc as extenal datastore for your data, for which BTW you might have to write the services to leverage it. You can check blog post How to configure Oracle 12c's Pluggable Database as External DataStorage for ThingWorx for sample services created, though the blog is for Oracle, you can use similar concept for other external RDBMS
There is one more option for 3rd party JDBC which you can test, though the extension is provided "as-is" and support is not extended via ThingWorx, but if you want you can test with JDBC from Maria Db using the JDBC Connector Extension, also available from ThingWorx Marketplace
Hope this helps.