mysql - How to set negative time difference value to zero -

if time difference result negative how set zero

select timediff('2016-01-29 12:28:18','2016-01-29 19:27:51') diff; 

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| -06:59:33 |

try this:

select if((time_to_sec(timediff('2016-01-29 12:28:18','2016-01-29 19:27:51'))/3600) < 0,0,timediff('2016-01-29 12:28:18','2016-01-29 19:27:51')) diff;