How to properly design database access?

Question

Database

Hello! very interesting for me and yet incomprehensible question.
I am making a web application for convenience at work with simultaneous access of 3 administrators ...
There are complex (nested) operations that make changes to several tables at once, but in turn, based on the conditions for executing previous queries to the database, and there are those that work directly with 1 table.
So I'm sitting and trying to figure out if there can be collisions when working with database tables at the same time? well, that is, when one admin launched the script, it threshes, and a second later the second admin accessed the table directly...
I read several open textbooks, but there are some ambiguous answers to such a question .. and in some it is not affected at all .. .
Can you answer me good people? maybe somehow you need to make a table of operations and take it from there in order of priority ??? how to do it right?

Answer 1

See the sections on transactional data processing; transactions and transaction isolation. Books have been written on this topic for at least half a century.
Collisions of course can be if you do not think about it during development. Sacrificing concurrency and forcing the execution of tasks in one thread - yes, it happens.