What material to study the database to choose?

Question

Database

Prompt good and most recent material or a book on databases and sql. I would like to start by studying history and theory, all the books I find are narrowly focused for some reason (relational databases or others), but I would like to figure out what databases are, what distinguishes them.

Answer 1

Stepika has free database courses

Answer 2

The story is simple.
When computers were large and RAM cost as much as an airplane, relational DBMSs were invented that stored data on disk and indexes in memory. They work fast, scale, optimize, store data in an easily described and structured form.
When RAM became cheaper, stylish fashionable youth databases like nosql appeared. Which are divided into stupidly living in the operative, that is, in fact, not being databases at all, but rather caching demons, such as the radish example, and "document-oriented" databases, which also live only if they fit entirely in the operative, such as Mongo . Due to the principle "we store everything as God puts it on our souls", each record contains not only the data itself, but also its structure - field names, nesting, etc. That is, if in a relational database you just look at the table header, and you understand , in which field you put this data, then in no-sql you go through ALL records in search of the desired field. And still the same data is eventually stored in dozens of different fields. Well, it adds more convenience that since all field names are stored with records, savvy developers abbreviate names to one or two letters to save memory. Which of course greatly facilitates the work with the base
Well, there are also specialized databases, for example, storing data not in rows, like relational ones, not in pampas, like nosql, but in columns, for fast aggregation. For example Clickhouse.
There is still every little thing, such as key-value storage, but I can’t raise my hand to call them a database. You do not call an array in the program a database.

Answer 3

When the basics are already there, then you can try the exercises on sql-ex