% corresponds to 0 or more characters, _ is exactly one character.
At least one character. Appendix G. Regular Expressions from MySQL manual is worth perusing before the interview.
SELECT MONTH(techpreparation_timestamp) from techpreparation_questions;
SELECT DATE_FORMAT(techpreparation_timestamp, ‘%Y-%m-%d’) from techpreparation_questions; A similar TIME_FORMAT function deals with time.
ADDDATE(techpreparation_publication_date, INTERVAL 3 MINUTE)