What is the correct way to write a query with DISTINCT or GROUP BY?

Question

MySQL

there is a request

(SELECT * FROM notification_role WHERE notification_role.role="curator") UNION (SELECT * FROM notification_user WHERE notification_user.user_id=15)

Question: how to combine 2 queries on the trigger field so that there are only unique values

Answer 1

SELECT DISTINCT [trigger] FROM notification_role WHERE notification_role.role="curator"
UNION 
SELECT DISTINCT [trigger] FROM notification_user WHERE notification_user.user_id=15

UNION already collects only unique attributes.
UNION ALL - everything.

Answer 2

What if there are a lot of sizes? What, dozens of different files to keep? Proceed from the situation, if there are a lot of styles and few sizes, then your option is suitable, and when there are few styles, but there are a lot of sizes, it’s easier to keep everything in 1 file!

Answer 3

And what prevents you from opening devtools and checking?
The browser loads all styles.