Re: [HACKERS] Outer joins
| От | Thomas Lockhart |
|---|---|
| Тема | Re: [HACKERS] Outer joins |
| Дата | |
| Msg-id | 3753FF09.F8035ECD@alumni.caltech.edu обсуждение исходный текст |
| Ответ на | Re: [HACKERS] Outer joins (Kaare Rasmussen <kar@webline.dk>) |
| Ответы |
Re: [HACKERS] Outer joins
|
| Список | pgsql-hackers |
> > select * from t1 left|right|full outer join t2 on t1.x = t2.x;
> Will this be correct?
> SELECT * FROM t1, t2, t3, t4 LEFT OUTER JOIN ON t1.x = t2.x,
> t1.x = t3.x, t1.x = t4.x;
Left outer joins will take the left-side table and null-fill entries
which do not have a corresponding match on the right-side table. If
your example is trying to get an output row for at least every input
row from t1, then perhaps the query would be
select * from t1 left join t2 using (x) left join t3 using (x) left join t4 using (x);
But since I haven't implemented it yet I don't have much experience
with the outer join syntax...
- Thomas
--
Thomas Lockhart lockhart@alumni.caltech.edu
South Pasadena, California
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