how to calculate duration time from start time and end time columns

[vanir88]

Hi,

i have columns like [start time], [end time], so i have to 'spent time'

for eg: data is like below. here total time has to calculate only if [start time]and [finish time] available

Start time	Finish time
02:45:23	03:10:15
06:26:00
12:57:54
15:09:12	17:40:39

[G3S]

if(not isnull([Start time]) and not isnull([Finish time]),[Finish time]-[Start time]) as spent time

[vanir88]

i used below condition but its throwing error like expected  ")"  can you please correct of anything wrong

if(not IsNull(Timestamp#([Time Finished],'YYYY-MM-DD hh:mm:ss.fff'))- not IsNull(Timestamp#([Time Started],'YYYY-MM-DD hh:mm:ss.fff')), ('YYYY-MM-DD hh:mm:ss.fff')) as Duration

Started Time	Finished Time
2023-01-03T02:45:23Z	2023-01-03T02:49:23Z
2023-01-03T06:26:00Z
2023-01-03T12:57:54Z
2023-01-03T15:09:12Z	2023-01-03T17:40:57Z

[G3S]

if(not IsNull([Time Finished]) and not IsNull([Time Started]),

Timestamp#([Time Finished]-[Time Started],'YYYY-MM-DD hh:mm:ss.fff')

,'YYYY-MM-DD hh:mm:ss.fff') as Duration

[vanir88]

it is not coming correctly, if [Time Finished] column is empty it has to show as empty only, and duration format is coming like below. 

the expected result is like for example in the above table the Duration should come as   00:04:00

[G3S]

if(not IsNull([Time Finished]) and not IsNull([Time Started]), ([Time Finished]-[Time Started])) as Duration

if this does not show in the format you require you can add the timestamp expression