Re: update - which way quicker?

On 2008-08-28, at 21:31, Emi Lu wrote:

> Good morning,
>
> Tried to compare Table1 based on Table2
>
> . update table1.col = false
> if table1.pk_cols not in table2.pk_cols
>
>
>
> For the following two ways, (2) always performs better than (1) right,
> and I need your inputs.
> ======================================================================
> ==
> (1) update table1
> set col = false
> where table1.pk_co1 || table1.pk_col2.... || table1.pk_colN
>
> NOT IN
>
> (select pk_co1 || pk_col2.... || pk_colN
> from table2
> )
>
> (2) ResultSet(rs) =
> select pk_col1||pk_col2... || pk_colN
> from table1
> left join table2 using (pk_col1..., pk_colN)
> where table2.pk_col1 is null
>
> Then for each rs record, do:
> update table1
> set col = false
> where col1||... colN in rs.value
>
> Thanks a lot!
>
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