How do I handle default values?

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How do I handle default values?

simflex-897410

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Points: 3881
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June 1, 2013 at 2:48 pm

#278124

Greetings experts,
I have 2 fieldnames on 2 different tables.
One fieldname is called SeatCapacity. This fieldname name has a value of 45 and it is on a table called Locations
Then there is another field called RemainingSeats on a table called tblMain.
tblMain table contains details of signups such as loginId of who signed up, course signed up for, date of training, etc.
This fieldname should contain an initial value of 45 as well.
Each time an individual signs up for a seat, 1 is substracted from RemainingSeats.
For instance, if RemainingSeats is 45 and I sign up for a seat, RemainingSeats should only be 44.
This goes on till RemainingSeats is 0 in which case, no one can sign up anymore.
Here are my issues right now.
1, how do I assign initial value of 45 to RemainingSeats?
I tried adding 45 to tblMain in design mode in ssms but I can't see this value.
2, When I tried doing an insert statement like:
Insert into tblMain(loginId, dateofCourse, courseName,RemainingSeats) VALUES(1,'2/12/2012','Test Course', (RemainingSeats - 1))
When I try testing this, I get the following error:
The name "RemainingSeats" is not permitted in this context. Valid expressions are constants, constant expressions, and (in some contexts) variables. Column names are not permitted.
How do I resolve these?
Thanks a lot in advance

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Sean Lange SSC Guru Points: 286590 More actions · Answer 1

The most straight forward way is to NOT store calculated data. You should just have to be calculated as you need it. AvailableSeats = InitialSeats - sum(RegisteredSeats).

The query you have will never work. You are doing an insert, during that insert RemainingSeats has no value. If you are deadset on storing calculated data you will have to a subquery. Storing data like that will come back to bite you. It is not a matter of if, it is a matter of when and how often.

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