Question

I had a table employeeswipe_tbl in SQL Server 2008 with these columns:

create employeeswipe_tbl swipepk int (
swipepk int primary ,
empid  int,
dateofswipe date ,
intime datetime,
outime datetime,
logduration  time
)

When employee login in the intime, empid, dateofswipe is entered and when log out the outime is updated against swipepk

Now what I want is when I update outtime the logduration will be automatically calculated like

logduration  = outtime - intime

I am thinking of a some ideas like a computed column or a trigger. Can anyone give a good option considering I am a beginner ?

Answer 1

A computed column is usually a better option than a trigger. Triggers can be disabled. A computed column is “always” correct:

create table employeeswipe_tbl (
swipepk int primary key,
empid  int,
intime datetime,
outime datetime,
dateofswipe AS CONVERT(date,intime) ,
logduration AS DATEDIFF(second,intime,outime)
)

As indicated in my comment, the difference between two datetimes would be a time span, not another datetime. There’s no time span type in SQL Server, so just keeping the difference in seconds is probably best – do any formatting of it into hours, minutes and seconds during display. This will make it easier if you need to, for instance, add together several rows worth of data.

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Side note – I was considering making dateofswipe a computed column also – isn’t it just the date part of intime?