In response to Craig Ringer :
> I don't understand what you want based on your description and your
> example results. What do you mean by "if the column `b' have the same
> value" ?
Additionally, don't hijack other threads by answer to an old message and
changing the subject. Your eMails contains a references-header for a old
thread, because ot this, your mail occurs in a foreign thread.
Andreas
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Andreas Kretschmer
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