Re: Newbie PL/SQL inquiry regarding existence check.

Mick,

A select count(*) will be expensive since all records will be accessed from the top of the table to the end of the table to get that count. You may want to look at the EXISTS function as an alternative. The function taks a SELECT statement as a parameter.

Dan Orwig

In article <343aed2c.1848618_at_news.psu.edu>,   zlm101_at_psu.edu (Zernan Martinez) wrote:
>
> I don't think so. The "rownum" column will be evaluated before the
> other conditions in the "where" clause.
>
> Zern
>
> On 7 Oct 1997 20:04:19 GMT, "Gerard H. Pille" <ghp_at_skynet.be> wrote:
>
> >You might try to add a "and rownum <= 1" to the where-clause.
> >--
> >Kind reGards,
> >
> >Gerard
> >(ghp_at_santens.be; ghp_at_skynet.be)
> >
> >Mick Davies <mdavies_at_elekom.com> schreef in artikel
> ><01bcd340$ad1b0c90$84e16acc_at_mdavies>...
> >> Respects to all Oracle experts.
> >> I would like to find the most processing efficient solution to the
> >> following:
> >>
> >> Assume a table of records.
> >> I would like to query this table for the existence of one or more records
> >> meeting a WHERE clause criterion, and set a local PL/SQL variable
> >> to 1 if ANY records exist, and 0 if NO records exist.
> >>
> >> For instance, I could use:
> >>
> >> Select count(*) into <local_var> From <Table> Where <criteria>;
> >>
> >> However, could this be a very costly query for a very large table?
> >>
> >> Is there a better way....anyone?
> >>
> >> Thanks in advance.
> >> Posting and e-mail reply would be nice.
> >>
> >> Mick Davies, mdavies_at_elekom.com
> >>

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