SQL if there is no data in the table?

Question

SQL

If there is no data in the table that I am looking for, then just do not perform this check.

SELECT * FROM service.ads, service.users, service.ads_photos
WHERE ad_id = 126 AND user_id = ad_creator AND ad_ad_id = 126

in the last check where ad_ad_id = 126 how to do this if there is no such value in this table, then just so that it is not processed