it depends on how many records are in each table.
if thare are more records in the table being deleted from than in the two tables in the subquery combined, use in. if its the other way around, test it with exists.
>
> From: "Naveen Nahata" <naveen_nahata_at_mindtree.com>
> Date: 2003/05/27 Tue AM 02:41:44 EDT
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Subject: RE: Alternative way to write delete query
>
> delete from table
> where column in (select col_a from table_b)
> or column in (select col_b from table_b)
>
> Can't say whether the performance will *really* be increased or not but
> 'explain plan' definitely looks much better :-)
>
> Regards
> Naveen
>
>
> > -----Original Message-----
> > From: Mark Richard [mailto:mrichard_at_transurban.com.au]
> > Sent: Tuesday, May 27, 2003 10:57 AM
> > To: Multiple recipients of list ORACLE-L
> > Subject: Alternative way to write delete query
> >
> >
> > Hi List,
> >
> > I'm having a mental blank and looking for suggestions... I'm
> > trying to
> > remember alternative ways to write the below query:
> >
> > delete from table
> > where column in (select col_a
> > from table_b
> > union all
> > select col_b
> > from table_b);
> >
> > Having said that, I don't mind if you simplify the nested
> > query down to
> > "select col_a from table_b" even. I just have a feeling that
> > I've seen an
> > equivalent query written totally differently but I can't
> > remember how. I
> > have a feeling it effectively allows more than one table to
> > be mentioned in
> > the delete without needing a nested query (like the options
> > available in
> > normal selects).
> >
> > Any suggestions?
> >
> > Thanks,
> > Mark.
> >
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Received on Tue May 27 2003 - 07:20:35 CDT
