From: | Zhenchang Xing <xing(at)cs(dot)ualberta(dot)ca> |
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To: | pgsql-novice(at)postgresql(dot)org |
Subject: | can connectby() deal with cyclic graph? |
Date: | 2004-09-24 17:34:24 |
Message-ID: | Pine.SOL.4.44.0409241115500.20730-100000@stauffer.cs.ualberta.ca |
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Lists: | pgsql-novice |
hi,
I am a newcomer to PostgreSQL and SQL as well. I am doing my thesis in
university. My topic is about software evolution. So I am often faced with
such questions as:
1) the supertype and/or subtype of class/interface. I read PostgreSQL's
docs and some previous mails about connectby(). I understand it can help
me answer this question. But do i have to give a specific 'start_with'?
how can I query things like "the supertype of all classes"?
2) I understand connectby() can handle hierarchy/tree structure. How
about cyclic graph? For example, i have several classes, A, B, C, D.
A uses B, B uses C, C uses D, and finally D uses A. Starting from class
A, can connectby() return me A uses B, A uses C, A uses D, and stop
when it detect D uses A?
thanks so much.
zhenchang
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