Salesforce’s product is technically is a relational database. Maybe it doesn’t perfectly fit the relational model that Edgar Codd theorized, but I don’t think any widely used database product does.

A crucial aspect of the relational database is that the tables have columns which refer to another table (e.g. AccountId) and this what they call “lookup relationships” or “master-detail relationships” in Salesforce.

Also, I recently learned that SQL has triggers too in case you want the same procedure to take place after an INSERT, UPDATE, etc.

In Salesforce everything is an API call with hard limits eg you can only return 200 records unless you hit the bulk api.

JOINS do not exist in Salesforce. Instead you have to create bridge tables. Even then you can only traverse a max of three objects at a time.

Please do not try to use Salesforce as a general database, you are only putting yourself in a world of hurt.