Database Literature?

Question

Database

Hello colleagues! The question is: what are the most relevant books to read in order to achieve a good level of understanding in databases? Interested specifically: SQL/MySQL/PostgreSQL.
At the moment, they already have about 1.5 years of experience working with MySQL and PostgreSQL. I can create databases, tables, I know and can work with basic commands (insert, update, delete, alter, create, inner join, etc.), I can create indexes, interconnected tables, but sometimes I feel the lack of a theoretical background, because I studied purely in practice all these cases (I remember little from the lectures since my studies). I would like to pump a little theory + of course practice: optimization; all sorts of complex selections, sorting and other skills in non-trivial queries.
What do you recommend to read? At the moment, I noticed the following set of literature:
- Alan Bewley "Learning SQL";
- Martin Gruber "Understanding SQL" (not too old? 1993 edition extremely confuses me, although the book is praised including on the toaster in other topics);
- E.P. Morgunov "PostgreSQL Basics of the SQL language".
Maybe there is something else? I would like the theory to be touched upon for a general understanding of what is happening, but also practice.

Answer 1

Alan Bewley is very simple, of course it's worth reading, but rather for streamlining current knowledge than obtaining new ones)
In terms of a deep understanding of MySQL, a complex but good MySQL book. Performance optimization. - allows you to look at many things from the side of "why it's better", and not "it's accepted".

Answer 2

Thanks everyone for the replies!
I'll start by studying the basic concepts of the relational model, generalizing the theory of the database, based on the recommendation in another topic on the toaster, according to the lecture notes of V. N. Lukin from MAI https://www.studmed.ru/lukin-vn-bazy-dannyh-konspe ... /
Next, I will move into the study of specific DBMS and database application methodologies.