Re: INSERT question

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On 2001 November 15 03:03 pm, Roland Roberts wrote:
> >>>>> "Jason" == Jason Earl <jason.earl@simplot.com> writes:
>
>     Jason> Even better, however, is to use the functions nextval() and
>     Jason> currval() like so:
>
>     Jason> INSERT INTO parent_table (data) values ('some data');
>     Jason> INSERT INTO child_table (parent, more_data)
>     Jason>         (currval('parent_table_p_key_seq'),
>     Jason>          'more data');
>
> The above is probably the best for a pure-SQL way with the caveat
> that it should be wrapped in a transaction or currval() may not be
> what you expect; i.e., another client may add a row and you get a
> value different from what you inserted.

Actually, I don't think you need the transaction.  currval() "may not be what 
you expect" in a very different way from what you're impling above!

Session1: SELECT nextval('test')    # 1
Session2: SELECT nextval('test')    # 2
Session1: SELECT currval('test')    # 1     !!!!!!!
Session1: SELECT nextval('test')    # 3

Kinda counter-intuitive, but fits the definition.

- -- 
Andrew G. Hammond     mailto:drew@xyzzy.dhs.org   http://xyzzy.dhs.org/~drew/
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"To blow recursion you must first blow recur" -- me
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