need better way than row_number()

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need better way than row_number()

shanghaigirl-1125377

Ten Centuries

Points: 1231
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November 25, 2009 at 11:25 am

#143259

I need to order 2 columns on a 10m+ row table with no indexes, and the query I have runs about 8 mins, how can I speed it up. thanks.
create table tmpT
(
model char(2),
date1 datetime,
date2 datetime,
date3 datetime
)
insert into tmpT
select 'm1', getdate() - 7, getdate() - 5, getdate() -4 union all
select 'm1', getdate() - 6, getdate() - 5 , getdate() -4 union all
select 'm1',getdate() - 5, getdate() - 5 , getdate() -4 union all
select 'm1',getdate() - 4, getdate() - 5 , getdate() -4 union all
select 'm1',getdate() - 3, getdate() - 5 , getdate() -4 union all
select 'm1',getdate() - 2, getdate() - 5 , getdate() -4 union all
select 'm1',getdate() - 1, getdate() - 5 , getdate()-4 union all
select 'm2', getdate() - 7, getdate() - 5, getdate() -4 union all
select 'm2', getdate() - 6, getdate() - 5 , getdate() -4 union all
select 'm2',getdate() - 5, getdate() - 5 , getdate() -4 union all
select 'm2',getdate() - 4, getdate() - 5 , getdate() -4 union all
select 'm2',getdate() - 3, getdate() - 5 , getdate() -4
select * from tmpT
select
t.model,
t.date1,
t.date2,
t.date3,
case when t.date1 < t.date2
then 0
when t.date1 = t.date2
then 1
else row_1
end as c1,
case when t.date1 < t.date3
then 0
when t.date1 = t.date3
then 1
else row_2
end as c2
from tmpT t left join (
select row_number() over (partition by model order by date1) + 1 as row_1, * from tmpT where date1 > date2
) t1
on t.model = t1.model and t.date1 = t1.date1
left join (
select row_number() over (partition by model order by date1) + 1 as row_2, * from tmpT where date1 > date3
) t2
on t.model = t2.model and t.date1 = t2.date1

Viewing 7 posts - 1 through 6 (of 6 total)

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Garadin One Orange Chip Points: 29613 More actions · Answer 1

Create a clustered index on (model, date1) ?

That alone would likely have a massive performance impact.

Seth Phelabaum

Consistency is only a virtue if you're not a screwup. 😉

Links: How to Post Sample Data[/url] :: Running Totals[/url] :: Tally Table[/url] :: Cross Tabs/Pivots[/url] :: String Concatenation[/url]

PhilPacha Hall of Fame Points: 3645 More actions · Answer 2

Perhaps this isn't the actual SQL you're using? Your 't1' and 't2' sub-queries don't contain a 'Model' column - and neither alias is used in the rest of the query. As it stands, it appears the two left-joins can be removed. Additionally, the 'row_1' and 'row_2' columns referred to in the CASE statements are not defined anywhere in the query. Or, am I missing something?

Garadin One Orange Chip Points: 29613 More actions · Answer 3

You're missing the else's in the case statements that point to the rownumbers in the left joins. You can actually copy/paste/run that in SSMS to see what it does(although the 'why' is very much still a mystery to me as well).

Seth Phelabaum

Consistency is only a virtue if you're not a screwup. 😉

Links: How to Post Sample Data[/url] :: Running Totals[/url] :: Tally Table[/url] :: Cross Tabs/Pivots[/url] :: String Concatenation[/url]

Jeff Moden SSC Guru Points: 1004292 More actions · Answer 4

shanghaigirl-1125377 (11/25/2009)
I need to order 2 columns on a 10m+ row table with no indexes, and the query I have runs about 8 mins, how can I speed it up. thanks.

If it needs an index, either add one yourself or get the DBA to do it. Just make sure the query is "pat" before you do.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

TheSQLGuru SSC Guru Points: 134017 More actions · Answer 5

1) you have no where clause - do you REALLY need to return all 10+M rows?

2) can you please provide expected output? I can't for the life of me figure out why you have multiple left joins here for a simple order by need...

Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service

shanghaigirl-1125377 Ten Centuries Points: 1231 More actions · Answer 6

thanks for all your replies, and sorry for my late response, I was away for a few days.

the left join query gave me the exact result that I wanted. It needs to compare 2 dates partitioned by each model, if date1 is earlier than date2 then assign 0, otherwise start ordering 1,2,3... same as date3. yes, real query has to order 10m records. I have added an index model + date1, it worked much faster, now is 1 min 20sec.