Question

In MySQL I am trying to select rows from a table that have a lock_dt older than 10 hours. How can I write this sql statement properly?

select phone from table where ((now() - lock_dt) < 10 hours)

Answer 1

SELECT phone
FROM table
WHERE lock_dt > NOW() - INTERVAL 10 HOUR

Using intervals is pretty handy. Also, I try to isolate the column so an eventual index can be used (sometimes, the RDBMS don’t know how to use an index with NOW() – lock_dt, even if there’s an index on lock_dt).

Also, the description of your problem contradicts your query. NOW() - lock_dt < 10 hours means the interval is less than 10 hours. That’s what my query do. You have to change > to < if you want more than 10 hours.