

SSCommitted
Group: General Forum Members
Last Login: Monday, March 23, 2015 7:13 AM
Points: 1,619,
Visits: 1,281


nick.mcdermaid (3/7/2010) Someone appears to have drawn some inspiration from your article.
http://subhrosaha.wordpress.com/
Yes it certainly looks that way  even the reference links are the same. A little credit would have been nice!
_________________________________ seth delconte http://sqlkeys.com




SSChasing Mays
Group: General Forum Members
Last Login: Thursday, March 26, 2015 12:31 PM
Points: 644,
Visits: 2,164


Seth Delconte (3/8/2010)
nick.mcdermaid (3/7/2010) Someone appears to have drawn some inspiration from your article.
http://subhrosaha.wordpress.com/
Yes it certainly looks that way  even the reference links are the same. A little credit would have been nice! He has been served.
EDIT: The comment I submitted is awaiting moderation. If he rejects it, this is what I wrote At least properly credit the appropriate article if you’re going to copy from it (not the author of this original article but on the same forum) <link back to the article here>
Gaby ________________________________________________________________ "In theory, theory and practice are the same. In practice, they are not."  Albert Einstein




SSCommitted
Group: General Forum Members
Last Login: Monday, March 23, 2015 7:13 AM
Points: 1,619,
Visits: 1,281


GabyYYZ (3/9/2010)
Seth Delconte (3/8/2010)
nick.mcdermaid (3/7/2010) Someone appears to have drawn some inspiration from your article.
http://subhrosaha.wordpress.com/
Yes it certainly looks that way  even the reference links are the same. A little credit would have been nice! He has been served. EDIT: The comment I submitted is awaiting moderation. If he rejects it, this is what I wrote At least properly credit the appropriate article if you’re going to copy from it (not the author of this original article but on the same forum) <link back to the article here>
Ahh thank you Gaby!
_________________________________ seth delconte http://sqlkeys.com




Forum Newbie
Group: General Forum Members
Last Login: Monday, February 7, 2011 7:26 PM
Points: 2,
Visits: 28


You're missing one really important point.
Using GUID's is fine, but when the primary key is a clustered index, then you end up with halforless empty data pages which creates a lot of I/O and useless, partially empty data pages.
When you use a GUID as a primary key, make sure it isn't a clustered index or you'll get dogpoor performance.
Ron




SSCrazy Eights
Group: General Forum Members
Last Login: Thursday, March 26, 2015 2:47 AM
Points: 9,928,
Visits: 11,242


rd_in_sd (3/14/2010) Using GUID's is fine, but when the primary key is a clustered index, then you end up with halforless empty data pages which creates a lot of I/O and useless, partially empty data pages. When you use a GUID as a primary key, make sure it isn't a clustered index or you'll get dogpoor performance. This point has been raised numerous times already in this thread...and the answer is always the same: use the NEWSEQUENTIALID in a default constraint to avoid this issue completely. Full pages, minimal pagesplits...globallyunique goodness.
Paul White SQLPerformance.com SQLblog.com @SQL_Kiwi




Forum Newbie
Group: General Forum Members
Last Login: Monday, August 23, 2010 9:31 AM
Points: 6,
Visits: 57


Ok, this isn't the most elegant solution, but is is a proper "Simple Random Sample" and is very fast
/* FAST Simple Random Sample from a source table using pseudo random number generator RAND()
Usage: Sample Size is set following the "select top"
Copy and paste more random value subqueries than the sample size If the sample size is more than 20% of the source table size, you may have to include many time the sample size of random value subqueries and if more than 50%, consider changing the query to exlude the random rows.
Modify the @SourceRowCount and the first part of the query for your source table name (dbo.phrases in this example)
A random seed is used, but a fixed one can be used if desired Advantages: Does not use NEWID for randomness, which is not technically a Random Number Genrator Is FAST, even when the source table is large Select 10 from 10 million in 6 seconds, 1000 in 8 seconds Does not rely on data page assumptions (see TABLESAMPLE) Disadvantages: Not TRUE random numbers See Also: http://msdn.microsoft.com/enus/library/aa175776(SQL.80).aspx Presents three methods for random samples 1) Cursors and RAND() Cursor Overhead 2) Rand( ROW ID) Bad randomness 3) NewID
http://msdn.microsoft.com/enus/library/ms189108.aspx Documentation for TABLESAMPLE 1) Can only be used on true tables, not linked, views, XML, etc 2) Samples pages, not rows, if pages contain correlated row its no longer a simple random sample
*/
/* Find the number of rows in the source table */ declare @SourceRowCount integer select @SourceRowCount=COUNT(*) from dbo.phrases
/* Initialize the random number generator with a random seed (or a particular seed) */ declare @d integer set @d=RAND() set @d=RAND(an integer)
/* Create Source table from the desired table and ROW_NUMBER() Join Source to a table of random values between Select top n from a slightly larger set */
select * from (select *, ROW_NUMBER() over(order by GETDATE()) as Row from dbo.phrases) as source, (select top 10 n from (select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n union all select convert(integer, RAND()*@SourceRowCount) as n) as tmp) as R where source.Row=R.n




SSCrazy Eights
Group: General Forum Members
Last Login: Thursday, March 26, 2015 2:47 AM
Points: 9,928,
Visits: 11,242





Ten Centuries
Group: General Forum Members
Last Login: Friday, March 27, 2015 8:39 AM
Points: 1,140,
Visits: 670


A nice alternative to RAND and one of which I wasn't aware. Thanks!



