On Sat, 22 Oct 2011, Marco van de Voort wrote:
In our previous episode, michael.vancann...@wisa.be said:
Ok, now I want to insert a record in my table and I would like to
obtain the auto-generated PrimaryKey
This is a classic problem, since SQL simply doesn't support this.
So all DBs do something else, for postgresql there are sequence objects that
can be queried, while other allow to return the id of the autogenerated
fields.
Afaik sqldb does not abstract this yet.
That's because it can't be abstracted correctly. There are 2 incompatible
mechanisms.
1. autogenerated fields (mysql, MS SQL server) which must be retrieved after
the insert using a special API.
2. or sequences, which must be generated manually before the insert (DB2,
Oracle, Firebird) using a special
API, but which may or may not be generated in an AFTER INSERT trigger.
In which case it's impossible to retrieve the sequence value after the
insert except by re-reading the record.
I don't know which mechanism postgresql follows.
A combination. Autogenerated, but the API call that the value must be
obtained from is basically the sequence object. (which also has different
operations).
Afaik Zeos manages to abstract this for all these dbs by having a sequence
object.
I fail to see how it can do that. E.g. the mechanism by Martin is just a trick to update
a field value after an insert/update. That's a fine/useful mechanism, but not what I'd call
'abstracting'.
But never mind. I think the trick is useful, and we should look into getting it
in SQLDB.
Michael.
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