How to write a simple query with IF ELSE in MySQL?

Question

PHP

Please write an example.
What I want:
if my SELECT query finds a unique ID, then I don't make an INSERT query. If it does not find it (the query returns nothing), then I make an INSERT query.
I don’t want to set a condition in php and make two requests, but immediately write everything in one for optimization.

Answer 1

insert ignore? Or something more difficult?