How to add a variable number of hours to a date in PostgreSQL?

Question

Apparently, PostgreSQL doesn't have DATEADD, because you can just use the + or - operators.

I need to add a number of hours to a date, which is accomplished like this:

date_field + interval '8.25 hour'  

Which is great, but I need the number of hours to come from a field in the table. Would be something like this:

date_field + interval start_time 'hour'  

I can't find anywhere how to do this. Is this actually impossible?

I don't mind resorting to ugly hacks like taking the field value and dividing by 3600, multiplying by 86400. Whatever I need to do, but I haven't found any way to do that either.

Answer 1

Since you want to add hours, it should rather be:

SELECT date_field + interval '1 hour' * start_time 

start_time can be any numerical value.
'1 hour' can be shortened to '1h'.
interval can be multiplied by a scalar.

Answer 2

Found the answer, in another SO question:

date + interval '1' minute * FLOOR(start_time * 60) 

Hope that helps anyone