Re: Easiest way to compare the results of two queries row by row and column by column

[Vik Fearing <vik.fearing@xxxxxxxxxx>]

On 06/21/2013 01:07 AM, Jeff Janes wrote:

On Thu, Jun 20, 2013 at 3:18 PM, Jason Long <mailing.lists@xxxxxxxxxxxxxxxx> wrote:

Can someone suggest the easiest way to compare the results from two
queries to make sure they are identical?

I am rewriting a large number of views and I want to make sure that
nothing is changes in the results.

Something like

select compare_results('select * from v_old', 'select * from v_new');

I'd run:

select * from v_old 

except

select * from v_new ;

And then 

select * from v_new

except

select * from v_old ;

Both should return no rows.

This is my solution as well.

However, if the queries can contain duplicate rows this will not detect differences in the number of times a row is replicated, i.e. if one query has a row 2 times and the other has it 3 times.  If you need to detect such cases, I'd probably \copy out each query to a file, then use system tools to sort and diff the files.

No need, just use EXCEPT ALL.

Basically, the following query should return nothing:

(TABLE v_old EXCEPT ALL TABLE v_new)
UNION ALL
(TABLE v_new EXCEPT ALL TABLE v_old);

--
Vik