How to exclude selections of one and a row of sql?

Question

PHP

Making a fetch from the database

SELECT * FROM table WHERE Type =:type AND DateTimeRequest < NOW() - INTERVAL 24 HOUR ORDER BY DateTimeRequest ASC LIMIT 1

Next, I update the time:

UPDATE table SET DateTimeRequest = NOW() WHERE Id = $id

If the script is run 2 times at the same time, then sometimes it selects the same line, thereby pulling out the same result, how to avoid this?

Answer 1

Use transactions

Answer 2

Do a mutable field check

Answer 3

Bad option: use lock.
for cron: flock
for mysql: https://dev.mysql.com/doc/refman/8.0/en/lock-table...
for postgresql: https://www.postgresql.org/docs/9.1/functions- admi...
A good option: a complete rewrite with the involvement of a competent developer