问题:

I need to calculate the time a user spends on site. It is difference between logout time and login time to give me something like "Mr X spent 4 hours and 43 minutes online". So to store the4 hours and 43 minutes i declared it like this: duration time NOT NULL

Is this valid or a better way to store this? I need to store in the DB because I have other calculations I need to use this for + other use cases.

回答1:

Storing it as an integer number of seconds will be the best way to go.

The UPDATE will be clean and simple - i.e. duration = duration + $increment
As Tristram noted, there are limitations to using the TIME field - e.g. "TIME values may range from '-838:59:59' to '838:59:59'"
The days/hours/minutes/seconds display formatting won't be hardcoded.
The execution of your other calculations will almost surely be clearer when working with an integer "number of seconds" field.

回答2:

I wouldn't use time as you would be limited to 24 hours. The easiest would just to store an integer in minutes (or seconds depending on the resolution you need).