Re: how to do 'deep queries'?
От | Daryl Richter |
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Тема | Re: how to do 'deep queries'? |
Дата | |
Msg-id | 433947F6.7060106@brandywine.com обсуждение исходный текст |
Ответ на | Re: how to do 'deep queries'? ("Anthony Molinaro" <amolinaro@wgen.net>) |
Список | pgsql-sql |
Anthony Molinaro wrote: > that query is 100% correct. > > it's just an equijoin (a type of inner join) between 3 tables. > > the syntax you show is how queries should be written and is more > representative of what a joins between relations really are: > Cartesian products with filters applied > > the ansi syntax, the explicit JOIN ... ON stuff is (imho) unnecessary, > useful only for outer joins since all the vendors did it differently. > Whether you feel that is unnecessary or not, it *is* the ANSI Standard and is thus, by definition, "how queries should be written." In addition to cleaning up the outer join issue, it was added to make the *intention* of the query clearer. Because others are likely to read your query many more times than you write it, clarity of intent *is* important. > what you have will work for postgreSQL, I used the syntax you show in my > book > for every single join recipe except for outjoins. > > are you seeing errors? > > regards, > Anthony [original snipped] -- Daryl "We want great men who, when fortune frowns, will not be discouraged." -- Colonel Henry Knox, 1776
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