Re: SQL Diff ?

On Saturday 25 August 2007 21:10:19 Ron Johnson wrote:
> On 08/25/07 21:51, Kevin Kempter wrote:
> > Hi List;
> >
> > I have a very large table (52million rows) - I'm creating a copy of it to
> > rid it of 35G worth of dead space, then I'll do a sync, drop the original
> > table and rename table2.
>
> What is your definition of "dead space"?
>
> Bad rows, duplicate rows, old rows?  Something else?

deleted rows that should have been cleaned up with vacuum, problem is the
client let it go so long that now I cant get a vacuum to finish cause it
impacts the day2day operations too much.  Long story, see my recent questions
on the performance list for more info.


>
> > Once I have the table2 as a copy of table1 what's the best way to select
> > all rows that have been changed, modified in table1  since the initial
> > laod from table1 into table2?
> >
> > Also I'll need to delete any rows in table2 that no longer remain in
> > table1.
> >
> > There is no change date column
> > I could do something like select * from table1 where col1 || col2 || col3
> > etc not in (select col1 || col2 || col3 etc from table2)
> >
> > but this would be ineffecient & slow.
> >
> > Anyone have a suggestion to do this in an efficient manner?
> >
> > Thanks in advance