The date addition and subtraction functions in mysql don't seem to quiet do this. I was wondering if anyone know a way I could do this in the query:

Say you have two fields, start_time, and end_time, representing the start and end of a period of time. Both are datetime datatypes. What I want is the logical equivalent of:

select end_time - start_time as duration from ....

I want the difference between those two, such that it would say "0 days, 4 hours" or something.