How Do I Make A Database?

Answering your question sideways - you shouldn't make a database. And you don't actually want to make a database.

Writing an actual database is a ridiculous amount of work, and usually only done by masochistic systems people (pdf). If you wanted to do it for your own self-education or fun, by all means go for it, but if your real goal is to build a service that happens to use a database, there are much easier ways to go about it.

If I'm looking to create a database that will, eventually, be able to store images, songs, and videos

What you're looking for is a specialized type of database commonly called an object store. These specialize in mapping a small string key (like a filename or a path) to a large binary blob (the file contents). If you've ever used Amazon S3, that's one example of such a system.

Some relational databases can fulfill this purpose, as well. Postgres, for example, has a system called TOAST that allows storing large file-like blobs directly in the database.

So you've got a database backend (I'd recommend Postgres; don't get me started on MongoDB) and you store all the normal data you'd need for your service there. Then, for your files, you can either store them directly in Postgres, using TOAST columns, or you can store them in a separate object store, such as S3 or Minio, then store a pointer / breadcrumb to the file in a Postgres column.

So for the latter approach (Postgres + an object store) you end up with something like:

> select * from my_files;
file_id  name     path
1        foo.txt  s3://some_bucket/1
2        bar.jpg  s3://some_bucket/2

Then your service code knows that when it adds a row to my_files, it first needs to upload the file to the object store and save the URL to Postgres, and when it wants to read a file, it needs to look up the URL in Postgres then pull it from the object store.

The downside of this approach compared to TOAST columns is that you now have distributed transaction problems (you have to make sure that if you delete a row from Postgres, you also delete the corresponding file from S3, and so on). The downside of the TOAST approach is that your database size will grow quite quickly - if you have 1 TB worth of files, you probably have 1 GB or less of actual non-file metadata describing those files, but you've gotta pay for the full 1 TB of database space. And everything else being equal, 1 TB of storage in S3 or another object store will be significantly cheaper than 1 TB of Postgres capacity.

Doing an optimized database is VERY difficult and usually takes years to make something usable in production. To do something that works fast, you will have to use compiled languages, not interpreted ones.

I think I can give you further advice if you tell me what type of database do you want to create (relational, key-value store, graph database, etc.) and what is the most important, what needs to be very fast.

Just for clarification, are you literally asking "how do I make a database" or are you asking "how do I make a database SaaS"?

As in, making a DB engine from scratch, or do you just want to set up a database server?

The former is not exactly easy, and you'll want to take a look at this tutorial, and at 500 lines or less - they implemented different kinds of simple databases in chapters 6, 7 and 10.

If the latter, what do you need from it? Postgres is fine, but you might just be able to make use of SQLite if your app is not heavy on the writing, which doesn't require you to set up anything - and, as someone else said already, you probably don't want to store large files inside of it. There's already the filesystem for that.

If I'm looking to create a database that will, eventually, be able to store images, songs, and videos, where should I start my homework?

If you just want to store them, you'll need a schema - what information about them do you want to keep? What relationships would there be? Do you want to be able to tag them? Put them into categories? Will these categories be flat or hierarchical?

Again, what do you need/want to do with it?

If you've used MERN, you've already hosted a database. You just delete everything that returns an actual web page and badda bing badda boom you've made a DaaS. A shitty one, but one all the same.

Your next question needs to be 'how do I make a good DaaS'. And for that my only answer is 'go to university' (and any answer that does not start here is feeding you bullshit), followed with 'implement 100 shitty attempts', followed with 'gather a team with the necessary skills' - because a good DaaS needs to handle scalability and security to a point where you aren't going to find the right skills in a single person unless that person has some solid industry experience under their belt.