Re: gnarly delete statement?

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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