Q:

TIMESTAMPDIFF Format Conversion (Hours and Minutes)

My SQL query is correct in answers alone but when it comes to the format it fails.  Like for example the conversion value to Hours and Minutes is 4 Hours and 30 Minutes... If I concat it with ' : ' (Colon which is the normal separator for hours and minutes) it only shows like this '43' instead of '4:30'.. One more example is when the conversion value is 0 Hours and 59 Minutes it only shows '59' instead of '0:59'
This is my SQL query: (XAMPP Control Panel and phpMyAdmin as Database)
SELECT 
TIMESTAMPDIFF(hour,ratedemand_datestart,ratedemand_dateend)
+ ":" + 
MOD(TIMESTAMPDIFF(minute,ratedemand_datestart,ratedemand_dateend),60) as 'Time Left' 
FROM `ratedemand`

A:

Numbers generally have their leading zeros concatenated.  You can fix this by using the LPad() function. 
SELECT 
    concat(
        LPad(TIMESTAMPDIFF(hour,ratedemand_datestart,ratedemand_dateend), 2, 0)
        , ":"
        , LPad(MOD(TIMESTAMPDIFF(minute,ratedemand_datestart,ratedemand_dateend),60), 2, 0) 
    )as 'Time Left' 
...

