How to don`t change the value of a computed column?

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I use the following formula for my computed column Delay :

SQL

(case [IsReturned] when (0) then datediff(minute,dateadd(day,[Time],[StartDate]),getdate())  end)

it works correctly when the IsReturned column is 0, but when this IsReturned column is 1 the Delay column becomes null and I don not want this value to become null. I need to change this formula that don`t change the delay value if IsReturned = 1.

Thanks

Posted 4-Jan-15 21:57pm

Pedram Parsian

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CHill60 · Answer 1 · 2015-01-04T22:00:00

Solution 1

Try this

SQL

delay = case when [IsReturned] = 0 then datediff(minute,dateadd(day,[Time],[StartDate]),getdate())  else delay end

Posted 4-Jan-15 22:00pm

CHill60

Comments

Pedram Parsian 5-Jan-15 4:04am

it will not work because it made a loop ...

CHill60 5-Jan-15 4:07am

What loop?? Works fine for me

Pedram Parsian 5-Jan-15 4:11am

Computed column 'Delay' in table 'Circulation' is not allowed to be used in another computed-column definition. it is the error.

CHill60 5-Jan-15 4:36am

Have you defined the computed column as "Persisted"?
Have you considered using a Function to calculate the value?
Does this have to be a computed column (i.e. could the delay be calculated as and when the database is queried)

Sumit Jawale · Answer 2 · 2015-01-04T22:01:00

Solution 2

hi Try this

SQL

(case [IsReturned] when (0) then datediff(minute,dateadd(day,[Time],[StartDate]),getdate()) else 1 end)

Posted 4-Jan-15 22:01pm

Sumit Jawale

Comments

Pedram Parsian 5-Jan-15 4:07am

hello, I don't want to replace 1. I want to keep the last value.

Sumit Jawale 5-Jan-15 4:12am

then use your column as it is.. I guess delay is your column which you want to keep as it is.

(case [IsReturned] when (0) then datediff(minute,dateadd(day,[Time],[StartDate]),getdate()) else delay end)

Pedram Parsian 5-Jan-15 4:29am

I already said, it doesn't work.

Sumit Jawale 5-Jan-15 4:35am

ok. Use ISNULL in your select
ISNULL((case [IsReturned] when (0) then datediff(minute,dateadd(day,[Time],[StartDate]),getdate()) end),delay)