Обсуждение: joining VIEWs

<font size="2">Given a view like:<br /><br /> create view view1 as<br /> select g.id as UserGroupId, s.uid as UserId,
s.timeas StartTime from stats s join groups g on g.uid = s.uid<br /><br /> and a SELECT like:<br /><br /> select
a.UserGroupId,b.UserGroupIdfrom view1 a<br /> full outer join view1 b on b.UserGroupId = a.UserGroupId<br /> WHERE
a.StartTime>= '2006-1-1' AND a.StartTime < '2007-1-1'<br />   AND b.StartTime >= '2005-1-1' AND b.StartTime
<'2006-1-1';<br /><br /> where there are 5695 rows in 2006 and 1 row in 2005, I expected to get a result set of 5695
rows,but instead got only 1 row (the common row in the 2 years).  This seems contrary to the definition of "full outer
join". Am I missing something?<br /><br /> Thanks,<br /> Brian Cox</font><p><hr size="1" />Talk is cheap. Use Yahoo!
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On Tue, 22 Aug 2006, Brian Cox wrote:

> Given a view like:
>
>  create view view1 as
>  select g.id as UserGroupId, s.uid as UserId, s.time as StartTime from stats s join groups g on g.uid = s.uid
>
>  and a SELECT like:
>
>  select a.UserGroupId,b.UserGroupId from view1 a
>  full outer join view1 b on b.UserGroupId = a.UserGroupId
>  WHERE a.StartTime >= '2006-1-1' AND a.StartTime < '2007-1-1'
>    AND b.StartTime >= '2005-1-1' AND b.StartTime < '2006-1-1';
>
>  where there are 5695 rows in 2006 and 1 row in 2005, I expected to get
>  a result set of 5695 rows, but instead got only 1 row (the common row
>  in the 2 years).  This seems contrary to the definition of "full outer
>  join".  Am I missing something?

The where clause is applied after the join. If you want to filter the rows
before/during the join itself you can use subselects in the from clause or
put the additional conditions in the on condition.