Re: Proper relational database?
От | Guyren Howe |
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Тема | Re: Proper relational database? |
Дата | |
Msg-id | 1ABF001D-62FD-4543-81DC-6AF568C5F251@gmail.com обсуждение исходный текст |
Ответ на | Re: Proper relational database? (Raymond Brinzer <ray.brinzer@gmail.com>) |
Ответы |
Re: Proper relational database?
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Список | pgsql-general |
On Apr 22, 2016, at 10:45 , Raymond Brinzer <ray.brinzer@gmail.com> wrote: > > Are there relational algebra expressions, or other operations > necessary to a truly relational database, which cannot be translated > into SQL? I'm not aware that there are, but I'd be interested to hear > of it. If there were, there's a good chance you wouldn't be able to > translate them into the parse tree, either. The fundamental storage model needs to at least be a bit different. In particular, relations can't allow duplicates. Youcould have nulls (Codd proposed two different forms of null IIRC: a single null value and two different null values),although they should be more principled than the mess they are in SQL. I am no expert on database optimization, but I understand that it is significantly easier to do query optimization in a properlyrelational database, as it forms a reasonably simple algebra, which can be optimized much as you would optimize evaluationof a numeric expression. Major gains from a proper relational store would be: - a better language, easier to parse, read and generate. Perhaps multiple equivalent query languages; - other storage models (distributed and eventually consistent, say); - simpler (in implementation and use); We may also get some degree of faster and other good things. It also might be implemented in such a way that it can run asa server or more like SQLite.
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