Checking the time in ORACLE APEX 5.1

Question

I'm am new to apex and I'm working on a food ordering application where customers are permitted to change their order details only up to 15 minutes after the order has been placed. How can I implement that ?

Answer 1

Create a validation on date item. Calculate difference between SYSDATE (i.e. "now") and order date. Subtracting two DATE datatype values results in number of days, so multiply it by 24 (to get hours) and by 60 (to get minutes). If that result is more than 15, raise an error.

Answer 2

To provide an alternative to Littlefoot's answer, timestamp arithmetic returns interval literals, if you use SYSTIMESTAMP instead your query could be:

systimestamp - order_date < interval '15' minute

or, even using SYSDATE something like:

order_date > sysdate - interval '15' minute

One note, the 15 minutes seems somewhat arbitrary (a magic number) it relies on the order not starting to be processed within that time limit. It feels more natural to say something like "you can change your order until the kitchen has started cooking it". There's no need for any magic numbers then and considerably less wastage (either of the customers time always waiting 15 minutes or of the kitchen's resources cooking something they may then have to discard).