can't understand what CLUSTERED property means

leugim

hi

what means exactly the CLUSTERED property in a nav key?

regards

ar4ijs

Google 4ever:
http://www.google.com/search?hl=en&rls=en&q=SQL+clustered+index

David_Singleton

Sure you should search Google to find out in general what a clustered index is, but your question is about the clustered index box in NAV.

In layman's terms "Clustered" means that all the data in the record is stored with this key. In Native datbase the Primary key can be compared to a Clustered index, because it stores all the data in the record. If you look at The Sales Line for example, the key Doc type, Doc No, Line No, includes with it Item no, description qty etc. so if you sort by Type,No and then find a record for a particular item, the server then has to go to the clustered index (doc typ, doc no, line no) to get other fields like say Description.

Unfortunately because Navision ALLWAYS does a SELECT *, it has to get every field even if you don't need them, so it ALLWAYS has to at some stage get the Clustered Index as well as the key it uses to execute the retrieval. (read more here : SELECT * in NAV on SQL

Optimizing the CLustered index, looks easy, but if you do it wrong you can cause a lot of problems. But of course no problems with playing with it in a test environment. So to answer your question, the tick box tells SQL which NAV key (or keys) need to contain all the data in the record.

leugim

wow! thanks david, this is what i call a good reply :!: :!:

thanks a lot, now i can explain what a clustered key is to my colegues

rgrds

David_Singleton

leugim wrote:

wow! thanks david, this is what i call a good reply :!: :!:

thanks a lot, now i can explain what a clustered key is to my colegues

rgrds

You are very welcome