Re: [SQL] Comparing two tables of different database

2009-05-01 Thread John Zhang
Hi Nicholas,

The query is across database query.  dblink is needed for that task.

Hope it helps,

John

On Thu, Apr 30, 2009 at 3:07 PM, Edward W. Rouse wrote:

>  Can’t you use this?
>
>
>
> select name from database2.sr_1 where name not in (select name from
> database2.pr_1);
>
>
>
> My test database VM isn’t running so I can’t test it, but I seem to
> remember that that’s how I did it for a few queries of that type. This is
> assuming the 2 databases are running on the same machine, like the way there
> is template0 as the default and you add addition databases to the same
> ‘instance’. If you are talking about 2 different database servers, then I
> have no idea.
>
>
>
> Edward W. Rouse
>
>
>
> *From:* pgsql-sql-ow...@postgresql.org [mailto:
> pgsql-sql-ow...@postgresql.org] *On Behalf Of *Nicholas I
> *Sent:* Thursday, April 30, 2009 6:12 AM
> *To:* Joshua Tolley
> *Cc:* Adam Ruth; Pawel Socha; pgsql-sql@postgresql.org
> *Subject:* Re: [SQL] Comparing two tables of different database
>
>
>
> Hi All,
>
>   For example,
>
> There are two database.   database1 and database 2;
>
>  database1 has a table called pr_1 with the columns, id,name and time.
>  database2 has a table called sr_1 with the_columns id,name and time.
>
>  i would like to find out the differences that is, find the names that
> are not in sr_1 but in pr_1.
>  we can achieve this by the query,
>
>  select name from sr_1 where name not in (select name from pr_1);
> the above query will work in case of two tables in the same database.
>
>
>  But the problem is, these two tables are in different database. i did
> not understand about the dblink.
>
> is there any exaples on dblink. can we do it without using dblink.
>
> -Nicholas I
>
>
>
>


Re: [SQL] Comparing two tables of different database

2009-05-01 Thread Wei Weng



On 05/01/2009 11:55 AM, John Zhang wrote:


Hi Nicholas,

The query is across database query. dblink is needed for that task.

Hope it helps,

John

On Thu, Apr 30, 2009 at 3:07 PM, Edward W. Rouse 
mailto:ero...@comsquared.com>> wrote:


Can’t you use this?

select name from database2.sr_1 where name not in (select name
from database2.pr_1);

My test database VM isn’t running so I can’t test it, but I seem
to remember that that’s how I did it for a few queries of that
type. This is assuming the 2 databases are running on the same
machine, like the way there is template0 as the default and you
add addition databases to the same ‘instance’. If you are talking
about 2 different database servers, then I have no idea.

Edward W. Rouse


How do you formulate the query using dblink?

Thanks
Wei


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