Can the database push messages directly to the mobile phone? Maybe, but I haven't heard of it yet.

Usually a web server is set up between the mobile terminal and the database server.

If you want to learn Android development, you must learn Java language before learning Android development.
You also need to learn to configure common web servers, such as tomcat, jetty, etc.
In addition, you need to learn the basic principles of databases, basic SQL syntax, and the use of a common database, such as MySQL.

This is just very basic, you also need to learn the HTTP protocol, database table design, JDBC, etc. . .

Is it because my understanding ability is too poor?
Or is the technology really too poor?
The database and the mobile terminal cannot be directly related. .
The database stores data, and the mobile terminal you mentioned should be used for display. Both of them should have a third party to read the data from the database and send it to the mobile phone
It is also called push

Push. Is it an app? Both Apple and Android have official push methods. You can also use third parties such as Goutiao etc.

As for the database. Then you just need to read it out. Then write the push code

The push you are talking about should be a WeChat page, an H5 page. H5 pages interact with databases. First, the mobile front-end is developed, and then a server-side language (backend) is needed, such as java.php. The interface is written and deployed on the server. First, connect the database and front-end, and secondly, learn database-related knowledge and master commonly used SQL statements

Let’s just talk about push, HTTP protocol related, tcp/ip, socket. If you want to get started, you can check out the open source xmpp framework