t2.timestamp > t1.timestamp?
he wants to delete the LATEST insert timestamp, right Paul?
- Regina Harter <rharter_at_emc-inc.com> wrote:
> Try this:
>
> Delete from my_table t1
> where a = 2 and exists
> (select 'X' from my_table t2
> where t2.a = t1.a
> and t2.b = t1.b
> and t2.c = t1.b
> and t2.d = t1.d
> and t2.timestamp < t1.timestamp)
>
> At 12:55 PM 11/1/01 -0800, you wrote:
> >Given a business rule that says a combination of three columns must
> be
> >unique if and only if a fourth column equals a certain value, and if
> >the table in question contains rows that violate this requirement,
> I'm
> >trying to write a single SQL statement that will remove the
> duplicates.
> > Of each set of duplicate rows, I'll delete the one with the latest
> >insert timestamp.
> >
> >Let's call the columns
> >
> >a b c d timestamp
> >
> >The combination of b, c, and d must be unique if a = 2.
> >
> >I can get the duplicate row values along with the latest timestamp
> via
> >
> >select max(tstamp), a, b, c from
> >my_table group by a, b, c having count(*) > 1
> >
> >But I can't figure out how to use that in a delete statement.
> >
> >Suggestions greatly appreciated!
> >
> >
> >Paul Baumgartel
> >
> >
> >__________________________________________________
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> Author: Regina Harter
> INET: rharter_at_emc-inc.com
>
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Received on Thu Nov 01 2001 - 20:20:46 CST
