INNER JOINS in sql-select.html
От | Stefan Weiss |
---|---|
Тема | INNER JOINS in sql-select.html |
Дата | |
Msg-id | 1503129.DJSjvup6Wb@weyoun.foo.at обсуждение исходный текст |
Ответы |
Re: INNER JOINS in sql-select.html
|
Список | pgsql-docs |
Hi. From <doc/html/sql-select.html>: | A CROSS JOIN or INNER JOIN is a simple Cartesian product, the same | as you get from listing the two items at the top level of FROM. CROSS | JOIN is equivalent to INNER JOIN ON (TRUE), that is, no rows are | removed by qualification. These join types are just a notational | convenience, since they do nothing you couldn't do with plain FROM | and WHERE. Is there really no difference between these two queries? SELECT blarg FROM ta, tb, tc, [...] WHERE ta.foo = tb.bar AND tb.bar = tc.baz AND [...] SELECT blarg FROM ta JOIN tb ON tb.bar = ta.foo JOIN tc ON tc.baz = tb.bar JOIN [...] I thought that by using the second form, you would be able to do 'explicit' joins, effectivly telling the planner in which order to join multiple tables (in case you have to join 10+ tables)? cheers, stefan
В списке pgsql-docs по дате отправления: