increment of key

Question

increment of key

rk-158886

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Points: 2
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July 15, 2004 at 3:52 am

#161684

I have the model# like 'r001','r002','r003','c001','c002','c003''c004'
i want to write a storeprocedure which will generate automatically the the next model# depend on the 'r'/'c'
say next time it has to generate 'r004'/'c005' while running my store peocedure next time

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Johan Bijnens SSC Guru Points: 135368 More actions · Answer 1

if that is what you need .... create a parameter table in which you keep your last or next value per keytype (r/c/...)

Isn't it the same for you application/user if you just have one running number (maybe identity / uniqueid) and then add the r or c as an attribute to your data ?

This way you have a meaningless key which may be more adaptable in the future.

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gljjr SSChampion Points: 10080 More actions · Answer 2

This is going to make your life miserable in the long run.

As Alzdba stated I would add an identity column to use as an alternate key for table and then use that number along with your modeltype to create the model# value. Otherwise you will need to design a function to parse out the model# into the separate parts and then get the max value used from that, or do as Alzdba stated and use a separate table that you store the last given value for each type in. Niether of these solutions scale very well though.

Please be advised that using identity columns with replication is a royal pain!

Gary Johnson
Microsoft Natural Language Group
DBA, Sr. DB Engineer

This posting is provided "AS IS" with no warranties, and confers no rights. The opinions expressed in this post are my own and may not reflect that of my employer.

Guy Haskell Ten Centuries Points: 1212 More actions · Answer 3

If you are stuck with an existing db design, you should be able to do something like this:

create function fnGetNextModelNo(@type nchar(1)) returns nvarchar(4) as
begin
declare @return nvarchar(4), @max-2 int
select @max-2=max(cast(substring(modelno,2,3) as int)) from models where left(modelno,1)=@type
set @return=@type+right('000'+cast(@max as nvarchar(3),3)
return @return
end

Then you can do:

select dbo.fnGetNextModelNo('r')

or

select dbo.fnGetNextModelNo('c')

to get the next number.

Be aware that you may need to have some sort of loop catering for duplicate key errors if you are expecting lots of concurrent record insertions.

Scalability Doug SSCertifiable Points: 5351 More actions · Answer 4

I had a similar situation and had to go the parameter table route and it was not that difficult. For each model number you will have a "last model id" in which you just need to increment to get the new number for that model. The reason the Identity column did not work for me was this: Each different model type was based on the previous. Model type 1 would go from RD001 to P001. Using the identity column caused gaps. If two models went to RD befor one went to P then the P model lost it's sequence ( RD001, P001, RD002, RD003, P004 ) Wrong! And then the next RD would be RD005 causing a gap and the users to ask what happened to RD004?

Needed (RD001, P001, RD002, RD003, P002, RD004&nbsp.