March 4, 2010 at 8:32 pm
Comments posted to this topic are about the item Sparse Columns
Saurabh Dwivedy
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March 4, 2010 at 9:48 pm
March 4, 2010 at 10:10 pm
Thanks Saurabh, I learned something about sparse columns today.
Jason...AKA CirqueDeSQLeil
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March 5, 2010 at 12:13 am
Good question....learnt from it...tnx
March 5, 2010 at 12:25 am
I can get clear idea for this.
Thanks,
Keyur Patel
March 5, 2010 at 12:25 am
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March 5, 2010 at 3:50 am
sorry for sounding stupid, but has anybody implemented sparse in his/her code ?
what was the reasoning behind.. is it really worth ?
March 5, 2010 at 7:52 am
This is good information. Thanks for the question.
March 5, 2010 at 9:22 am
Guess I am a bit confused by the question
A sparse column must be nullable and cannot have the ROWGUIDCOL or IDENTITY properties. A sparse column cannot be of the following data types: text, ntext, image, timestamp, user-defined data type, geometry, or geography; or have the FILESTREAM attribute.
I'm not sure how something is "defined on them", it may have had a meaning different than the one I read into it. It is clear that a Sparse Column cannot have a Filestream attribute.
There have been times in the past when my sparse sql skills prompted me to look at a Union statement when trying to compare two values that would have best been seen in a left join. The sparse column would have come in handy. It is a good topic. I wonder if we can just reword it slightly... maybe "Can a sparse column have a FileStream Attibute?"
Jamie
March 5, 2010 at 7:04 pm
ziangij (3/5/2010)
sorry for sounding stupid, but has anybody implemented sparse in his/her code ?what was the reasoning behind.. is it really worth ?
Implementation of the sparse column makes sense only if the data in the column is, well, sparse. This is because it takes more space to store not null values in the sparse columns. For example, character types, such as char and varchar need twice as many bytes to store not null data if the column is defined as sparse. For those types only if 60% or more of all records are nulls then it makes sense to define the respective columns as sparse. For example, many databases storing consumer/customer/person records might end up having a column storing data for so-called address line 2 which will not have any data in the majority of records, which makes such column a good candidate to be defined as sparse.
Oleg
March 7, 2010 at 9:47 am
Oleg Netchaev (3/5/2010)
ziangij (3/5/2010)
sorry for sounding stupid, but has anybody implemented sparse in his/her code ?what was the reasoning behind.. is it really worth ?
Implementation of the sparse column makes sense only if the data in the column is, well, sparse. This is because it takes more space to store not null values in the sparse columns. For example, character types, such as char and varchar need twice as many bytes to store not null data if the column is defined as sparse. For those types only if 60% or more of all records are nulls then it makes sense to define the respective columns as sparse. For example, many databases storing consumer/customer/person records might end up having a column storing data for so-called address line 2 which will not have any data in the majority of records, which makes such column a good candidate to be defined as sparse.
Oleg
Thanks Oleg for providing a relevant example. Appreciate it.
@jamie - You've got a point there. I think the wording could have been more precise. I am studying for the SQL Server MCTS exam and this topic (on sparse columns) came up somewhere. That's how I came up with the question. Not everything will be relevant to everyone. There are some who just like to learn something for the sheer academic pleasure the learning provides. For some it could turn out into a helpful idea to be implemented in a crux situation, perhaps.
Truthfully, I do SQL Server only because I like the subject matter and want to learn it. I have never used Sparse Columns in my actual experience.
This was my first attempt at posting a question on this wonderful forum. I hope to continue learning and wish all of you the same.
Regards
Saurabh
Saurabh Dwivedy
___________________________________________________________
My Blog: http://tinyurl.com/dwivedys
For better, quicker answers, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537
March 7, 2010 at 2:31 pm
Nice question. I hadn't a clue, so today I made time to read all the BOL stuff about FILESTREAM, so today I have learnt more than most days.
Can't imagine why MS decided that columns with filestream values couldn't be sparse, though.
Tom
March 30, 2010 at 8:16 am
Lucky guess today. Thanks for making me think about it, though can't imagine it will ever be useful.
Paul White
SQLPerformance.com
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@SQL_Kiwi
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