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funketekun
Constraint Violating Yak Guru
491 Posts |
 Posted - 2006-06-02 : 16:29:59
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| when do you use them?i only know you use clustered when you have million of records. So once the table has been indexed, query statement is able to retrieve the recordset faster.what about nonclustered? |
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Kristen
Test
22859 Posts |
Posted - 2006-06-03 : 02:16:54
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| "i only know you use clustered when you have million of records"Nope, that's not a criteria I would use.A clustered index means the data itself is held "within" the index. Thus there can only be one per table. It is great for processing a range of records - because as you "next" through the records they are adjacent in the data file. Most commonly used for the Primary Key, although it doesn't have to be.Non clustered indexes are therefore used for all the other indexes. They require two I/O's to get to the record - one to read the index record and a second to read the data record; this can mean that in order to "next" through the records whilst SQL is walking sequentially through the index it may be jumping around all over the data itself.Kristen |
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funketekun
Constraint Violating Yak Guru
491 Posts |
Posted - 2006-06-03 : 14:25:26
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| so when do u use clustered and nonclustered.?" |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2006-06-03 : 15:01:53
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| Interview question?CODO ERGO SUM |
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eyechart
Master Smack Fu Yak Hacker
3575 Posts |
Posted - 2006-06-03 : 23:36:24
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quote:
Originally posted by funketekun
so when do u use clustered and nonclustered.?"
Kristen gave you a reason.we have trouble answering these types of questions because:1. this is usually homework2. if it isn't homework, it is an interview question3. Books online contains this info4. if you can't find info in BOL, then googling "clustered index sql server" will certainly work-ec |
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clustered and nonclustered index