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From Rick Hillegas <Richard.Hille...@Sun.COM>
Subject Re: territory-based collations and optimizations for the LIKE operator
Date Mon, 25 Aug 2008 18:39:37 GMT
Daniel John Debrunner wrote:
> Mamta Satoor wrote:
>
>>  > On 8/25/08, Rick Hillegas <Richard.Hillegas@sun.com> wrote:
>
> >> 2) The LIKE operator has Derby-specific semantics. The Derby-specifics
> >> semantics return a subset of the rows which qualify under the ANSI 
> rules.
>
>>
>> For 2), we have jira entry DERBY-2793
>
> DERBY-2793 is not about incorrect rows being returned is it, it's 
> about following the rules for when LIKE can be used with different 
> collations?
>
> Rick, why do you believe that Derby will return a subset of the rows, 
> it doesn't seem to follow from any of the other posts in this thread?
>
> Dan.
Hi Dan,

Thanks for helping me puzzle through this. Consider the example we are 
working with, a collation in which 'z' = 'xy'. What happens with the 
following insert:

  insert into T(A) values ( 'zcb' ), ( 'xycb' )

followed by this query:

  select * from T where T.A like 'xy_b'

If I  understand what is being said, it seems like the following 
happens: the ANSI rules return both rows but Derby returns only ( 'xycb' )

Thanks,
-Rick

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