topic select distinct in Application Development and Automation Discussions

select distinct

Former Member — Mon, 24 Nov 2008 12:38:41 GMT

Moved to correct forum by moderator

HI All,

can i write the querry as below. Is it good for performance issue?

SELECT DISTINCT vkorg spart FROM tvta

INTO TABLE lt_spart

WHERE spart IN spart

AND vkorg IN r_vkorg.

Edited by: Matt on Nov 24, 2008 2:40 PM

Re: select distinct

Former Member — Mon, 24 Nov 2008 12:40:13 GMT

Is this part correct?

WHERE spart IN spart

Re: select distinct

Former Member — Mon, 24 Nov 2008 12:44:23 GMT

yes that is correct

Re: select distinct

christine_evans — Mon, 24 Nov 2008 12:49:25 GMT


> HI All,
> 
> 
> can i write the querry as below. Is it good for performance issue?
> 
> SELECT DISTINCT vkorg spart FROM tvta
>     INTO TABLE lt_spart
>     WHERE spart IN spart
>       AND vkorg IN r_vkorg.

If your TVTA table contains as few entries as ours does (only 6) then the performance of any type of select will be fantastic. Performance is always affected by data quantities. There is nothing wrong with using DISTINCT if that is what you want to do.

Re: select distinct

Former Member — Mon, 24 Nov 2008 13:31:20 GMT

I think DISTINCT is nothing to do with the performance, the difference of using it or not is whether you

want repeat data.

Re: select distinct

Former Member — Mon, 24 Nov 2008 13:38:49 GMT

Yes it is correct. Select Distinct will only remove the duplicate entries in your selection if there are any in you dbtable.

Thanks,

Jayant

Re: select distinct

rainer_hbenthal — Tue, 25 Nov 2008 14:08:31 GMT


> Yes it is correct. Select Distinct will only remove the duplicate entries in your selection if there are any in you dbtable.
> 
> > Jayant

Yes, and to do so in a quick way, the select is "enriched" by the order by clause internally. It might be better to read everything into an internal table, sort this one and then do an delete ... duplictaes.

I would take this into consideration and compare the runtime analysis of both ways. Order by (even implicit ones) can cause a lot of performance issues when done on the table.