Cleveland DBA

SQL Server administration in Cleveland, OH

Stuff I learned … yesterday – statistics

Yesterday was a pretty full day between training and the ONSSUG June meeting immediately afterwards, so I didn’t get a chance to blog.  Anyway, I did learn something yesterday, but it didn’t come from the class I’m taking.  Erin Stellato (blog | twitter) gave a great presentation at ONSSUG about statistics.  I really wish she’d had more time because it was simply crammed with good information. 

Anyway, two key things I learned:

  1. Multicolumn statistics – Just what they sound like, statistics over multiple columns.  These are created by default when you create a composite index, but you can also create them yourself without an index using the CREATE STATISTICS command.  Helpful when you have queries that filter on multiple columns where no index exists.
  2. Filtered statistics – You can also put a filter on your statistics.  This is useful when you have a very large table but normally only query on a small subset of rows.  If these rows are highly selective, creating filtered statistics will help the optimizer choose the best path.

For more information on these 2 features or on statistics in general, check out Books Online.

Advertisements

June 8, 2011 - Posted by | Features, SQL Tuning | ,

No comments yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: