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From "Bernd Ruehlicke" <BRuehli...@lgc.com>
Subject RE: Inserting values in an identity column
Date Tue, 08 Mar 2005 17:55:45 GMT
Yes, but (in my personal opinion) it would be even better if we had a
global sequence generator like Oracle, MS SQL etc

See also http://issues.apache.org/jira/browse/DERBY-103

Than a user does not need to worry about this and just create a usual
colum which will support altering. The price is of course that you have
to insert the value yourselfe into this coulm but you may than use a
function like  "mySequence.nextval". This makes also sure that every
single row in your database (if each table has an identity) has a unique
key - in all of the database. This becomse pretty handy if a table holds
the key and name of other table(s) - generically. Like 

MyTable
table_id       VARCHAR
...
Source_ID      VARCHAR   (if a text string is used as sequence key)
Source_Table   VARCHAR  (name of source table)
...
...

If you only had column identifiers you will have scenarious where
"Source_ID" is the same for 2 differnt tables ! That is not possible
when using a global sequence.

... anyhow ... just some words for discussion.

B-)



> -----Original Message-----
> From: Kathey Marsden [mailto:kmarsdenderby@sbcglobal.net] 
> Sent: Tuesday, March 08, 2005 11:38 AM
> To: Derby Discussion; Derby Development
> Subject: Re: Inserting values in an identity column
> 
> Christian,
> 
> Could you please file a Jira entry for this?  I am hoping 
> there someone in the Derby development community that has 
> time to take up this issue and propose and implement a 
> solution.  It seems to me that this is a serious hindrance to 
> migration to Derby that would be good to resolve sooner 
> rather than later.
> 
> You can file it as an "Improvement"  in Jira at:
> http://issues.apache.org/jira/secure/CreateIssue!default.jspa
> 
> Thanks
> 
> Kathey
> 
> Trevor Squires wrote:
> 
> > Hi,
> >
> > I asked this very question last week (or so) for pretty 
> much the same 
> > reason.
> >
> > It doesn't appear that you can alter the table to make it 
> an identity 
> > column after creation (which was my first idea).  I was 
> also unable to 
> > find any way to switch off the identity feature temporarily either.
> >
> > One person suggested that derby ought to support something like 
> > "generated by default as identity" which makes sense - although I'd 
> > rather be able to just switch on and off the current behavior for 
> > loading of dumps and pre-population.
> >
> > In order to get my project out the door I ended up converting the 
> > logic to update/select rows in an "identities" table that I manage 
> > myself.
> >
> > HTH,
> > Trevor
> >
> > Christian Rodriguez wrote:
> >
> >> Hi everyone,
> >>
> >> I am trying to import data from a mysql dump file. 
> Basically, I need 
> >> to insert values in tables. Some of the tables in mysql include 
> >> auto_increment columns, that I have translated to 
> "generate always as 
> >> identity" in derby. Now... the mysql dump file has values in those 
> >> columns, and I get an error when trying to insert a value into an 
> >> IDENTITY column in derby. How can I do this?
> >>
> >> I have a couple of ideas, but none work:
> >>
> >> 1. I could define the column as a regular column (not 
> identity) and 
> >> after the values have been populated I could try to ALTER 
> the column 
> >> in the table to make it an identity column, but this last 
> part doesnt 
> >> seem posible.
> >> 2. Is there another way to implement "autoincrement" in derby?
> >> 3. Is it posible to disable the "identity" feature until 
> all values 
> >> have been populated?
> >>
> >> Any other ideas?
> >>
> >> Of course, I could let derby generate values for that 
> identity column 
> >> and then map the original values with those, and touch all the 
> >> references in the other tables and convert them to the new 
> identity 
> >> values, but that doesnt seem like a lot of work... and Im 
> getting the 
> >> feeling there should be a more reasonable way to import 
> "dumps" from 
> >> other databases...
> >>
> >> Thanks for any help you can give me,
> >> Xtian
> >
> >
> >
> 
> 

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