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What is a bitmap in sqlserver ?what does bitmap actually contain.

Question
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hi,
I have read in some article that, null values are maintained using bitmap.but i cant get what exactly is bitmap and what is purpose?
Please do reply.
Regards
Chaithu
Friday, June 10, 2011 5:18 AM
Answers
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Check out this similar post on bitmap indexing & filtering: http://social.msdn.microsoft.com/Forums/en-US/sqldatawarehousing/thread/3b7fc3a0-32e2-4c73-99c1-1357ebcc4753
~manoj | email: http://scr.im/m22g
http://sqlwithmanoj.wordpress.com
MCCA 2011- Marked as answer by WeiLin Qiao Monday, June 20, 2011 12:58 PM
Friday, June 10, 2011 7:16 AM -
The null bitmap exists for each record or row. Paul Randal has some great blog posts that explain this:
http://www.sqlskills.com/BLOGS/PAUL/post/Search-Engine-QA-27-How-does-the-storage-engine-find-variable-length-columns.aspx
http://www.sqlskills.com/BLOGS/PAUL/post/A-SQL-Server-DBA-myth-a-day-(630)-three-null-bitmap-myths.aspx
http://www.sqlskills.com/BLOGS/PAUL/post/Misconceptions-around-null-bitmap-size.aspx
http://www.sqlskills.com/BLOGS/PAUL/post/Inside-the-Storage-Engine-Anatomy-of-a-record.aspxJonathan Kehayias | Senior Consultant, SQLSkills.com
SQL Server MVP | Microsoft Certified Master: SQL Server 2008
Feel free to contact me through My Blog or Twitter. Become a SQLskills Insider!
Please click the Mark as Answer button if a post solves your problem!- Marked as answer by WeiLin Qiao Monday, June 20, 2011 12:58 PM
Monday, June 13, 2011 2:44 AM
All replies
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Hi tibork,
What is scope of the bit map.Like will it on the table or will it be for each row?
regards
Chaithu
Friday, June 10, 2011 6:50 AM -
Check out this similar post on bitmap indexing & filtering: http://social.msdn.microsoft.com/Forums/en-US/sqldatawarehousing/thread/3b7fc3a0-32e2-4c73-99c1-1357ebcc4753
~manoj | email: http://scr.im/m22g
http://sqlwithmanoj.wordpress.com
MCCA 2011- Marked as answer by WeiLin Qiao Monday, June 20, 2011 12:58 PM
Friday, June 10, 2011 7:16 AM -
The null bitmap exists for each record or row. Paul Randal has some great blog posts that explain this:
http://www.sqlskills.com/BLOGS/PAUL/post/Search-Engine-QA-27-How-does-the-storage-engine-find-variable-length-columns.aspx
http://www.sqlskills.com/BLOGS/PAUL/post/A-SQL-Server-DBA-myth-a-day-(630)-three-null-bitmap-myths.aspx
http://www.sqlskills.com/BLOGS/PAUL/post/Misconceptions-around-null-bitmap-size.aspx
http://www.sqlskills.com/BLOGS/PAUL/post/Inside-the-Storage-Engine-Anatomy-of-a-record.aspxJonathan Kehayias | Senior Consultant, SQLSkills.com
SQL Server MVP | Microsoft Certified Master: SQL Server 2008
Feel free to contact me through My Blog or Twitter. Become a SQLskills Insider!
Please click the Mark as Answer button if a post solves your problem!- Marked as answer by WeiLin Qiao Monday, June 20, 2011 12:58 PM
Monday, June 13, 2011 2:44 AM