Re: Difference in columns

"Gurjeet Singh" <singh.gurjeet@[EMAIL PROTECTED]
> writes:
> On Sun, May 11, 2008 at 11:47 PM, Craig Ringer
<craig@[EMAIL PROTECTED]
>
>> If you cannot assume that, you can use a subquery with limit and order
>> by to obtain the next record:
>> 
>> SELECT
>> a.ts,
>> (SELECT b.size FROM x b WHERE b.ts > a.ts ORDER BY b.ts ASC LIMIT 1)
>> - a.size AS difference
>> FROM x a;
>> 
>> ... but that'll be really slow for any significant number of entries.

> not really... if you have an index on the TS column.

The OP said this was a view, so it may well not have any easy way to
provide such an index.

			regards, tom lane

-- 
Sent via pgsql-sql mailing list (pgsql-sql@[EMAIL PROTECTED]
)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-sql