There is no super quick way to do that.
Are you looking to do it just for your migration, or to keep this behavior
in the future.
What I would do is use a fifth table that contains the next value for the
incremental counter.
Every time you need one or several IDs, you do use a stored proc to get the
next value.
What's important when doing that is thinking about concurrency.
so you would have a code that in transact sql would look like
proc getNextId(@numberOfIds int)
declare @returnId int
update next_id
set @returnId = nextId
, nextId = nextId + @numberOfIds
return @returnId
go
Something like that normally ensure that the table is updated *at the same
time* the value is returned to you (i.e. operation is atomic).
I guess you can do something like that on the application server layer too,
but then you do need to continue to think about multithreading, server
restart and things like that that can get tricky.
But to conclude on this point, having such a need normally means that your
datamodel is not clean. If those table share a key that needs to be unique
across tables, it means most likely that this key has the same semantic for
all 4 tables. Therefore it should most likely be just one table (maybe with
some extensions tables filled depending on the row, but still all should
start with a single table).
On Tuesday, June 26, 2012 8:48:23 PM UTC+2, ritesh ranjan wrote:
>
> Hi,
>
> I want to make a particular existing column unique. I have to same name
> column in 4 tables. I have created a new migration but not sure what to
> write inside
>
> *def up*
> * ...........*
> * ...........*
> *end
> *
>
>
> I am using rails 3.2.1. Please help.
>
> --
> Regards
> Ritesh Ranjan
> iPhone Developer & Designer
> tapisfun.com
> Follow me @ Twitter <http://twitter.com/#!/tapisfun>
>
>
--
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Talk" group.
To view this discussion on the web visit
https://groups.google.com/d/msg/rubyonrails-talk/-/3cmtAyLX6P4J.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en-US.
