Only show hours in MYSQL DATEDIFF

Precision-first approach

Precision is paramount when dealing with time, these points ensure that your calculations are on the dot:

Leveraging UNIX_TIMESTAMP

Another way to get the hour difference is subtracting UNIX_TIMESTAMP values and dividing the result by 3600:

-- When it's UNIX time, every hour counts
SELECT (UNIX_TIMESTAMP(end_time) - UNIX_TIMESTAMP(start_time)) / 3600 AS hours_difference
FROM your_table;


Note: UNIX_TIMESTAMP returns time as UNIX timestamp, which are seconds since the '1970-01-01 00:00:00' UTC.

Beware the Ides of Midnight

When start_time and end_time spans past midnight, TIMEDIFF returns negative hours:

-- The eerie hour past midnight, where hours turn negative
SELECT HOUR(TIMEDIFF(end_time, start_time)) AS hours_difference
FROM your_table;


The - sign means start_time is larger than end_time. To avoid such spooky results, always feed the later timestamp as end_time.

Tunnel vision focus on precision

When it comes to time, the difference of a moment is all that matters. Let's dive deeper into nuances:

Handling Date Boundary with TIMESTAMPDIFF and TIMEDIFF

The solution to time difference insensitivity towards date boundary is to use TIMESTAMPDIFF. It returns the hour difference as an integer, irrespective of the date boundary.

So unlike TIMEDIFF, TIMESTAMPDIFF isn't afraid of crossing that date boundary!

TIMEDIFF: Minute Precision Maestro

For short periods that do not cross date boundaries, TIMEDIFF followed by HOUR() is more suitable:

-- TIMEDIFF - For when every minute counts
SELECT HOUR(TIMEDIFF(end_time, start_time)) as hours_difference
FROM your_table;


Note: Keep an eye for negative results, TIMEDIFF is sensitive

Tricky time caveats to remember

Time is simple until it isn't, let's explore some oft-forgotten fuse-blowers:

Time Zone and Daylight Saving Time

Beware of the time zone nuances and daylight saving time, they can throw your calculations off balance.

Leap Seconds

While leap seconds don't often show up at parties, when they do, they come uninvited. MySQL does not consider leap seconds, be aware when precision is key.

Overflow and Underflow

“Always expect the unexpected” and plan for potential overflow or underflow. Be cautious when the result exceeds a typical integer or decimal data type range.