Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

The SQL Server documentation for sp_updatestats states that:

If 'resample' is not specified, sp_updatestats updates statistics by using the default sampling.

How exactly does SQL Server calculate the default sample size?

share|improve this question

1 Answer 1

up vote 1 down vote accepted

That's a good question. If you're interested in statistics, you might want to give Elisabeth Redei's excellent blog post a read:

Lies, Damned Lies and Statistics

It explains that, as the table size increases, the default sampling rate becomes insufficient to accurately represent the table's contents. It also provides a formula that she states is used in calculating the default sample set size (Rowmodctr 500 + 20% of total rows).

share|improve this answer
    
that's wrong, is the formula to determine if a statistics is out dated and then fires un update. the default sample size must be calculated with some other formula that I'm searching too. –  user208693 Feb 9 at 12:05

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.