Converting Excel formula to PHP or MySQL Query

Question

I'm trying to convert an excel scoring program and this one formula is driving me nuts. so this is the excel formula =IF(AD4<AE4,AE4-AD4,0) and I have been stumped for a little bit. I have looked at, and tried a few sample formulas for both PHP & MySQL, but I keep receiving syntax errors, unexpected if or else in the code.

So what the formula is checking to see if the elapsed time is under a set time, and if so, calculates the difference between the 2 fields and displays the outcome in time format hh:mm:ss.

This is the latest SQL query I tried:

Select *
       if (`Under Time`<`Speed Fault`,0) 
       else { (`Time Elapsed`-`Speed Fault`)} As Under Time 
from time_db

Answer 1

In sql , you can use case :

Select *,case when (UnderTime<SpeedFault) 
              then 0 
              else TimeElapsed - SpeedFault end As UnderTime 
from time_db

Answer 2

SELECT *,
       GREATEST(`Time Elapsed`-`Speed Fault`, 0) AS `Under Time`
FROM time_db;