Re: SQL question (Autoincrementing value.)

Ron Stow wrote in message <86vd6a$je$1_at_neptunium.btinternet.com>...
>I am access a database for a Workflow system that records a historic list
 of
>events on 'Work Ojcects' in a History table, the problem is the system only
>stores the 'After Image' and a lot of the results we whant require
>specifying criteria if the before and after the event has taken place. To
>match records in SQL it would be easier if they where incrementing field
>value that I could join using (b.ID = a.ID+1)
>
>***How do I insert an incrementing field value in an new table?***
>
[cut]

Generating unique Integer IDs is not an innate part of SQL, consequently each vendor has it's own way of generating such. Oracle uses an object called a sequence which guarantee to deliver a unique ID irrespective of simultanious enquiries. This object could be interrogated in a BEFORE INSERT trigger to get the unieue ID, or the inserter could get it himself with a SELECT <seq-name>.nextval FROM DUAL. You should consult the documentation on your particular DBMS regarding sequence-like features.

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Thomas