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Index Classification, Indexes Summary, Views, Security, Efficiency, Characteristics of Views, 3 level schema architecture are the main points of this lecture.
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Clustered vs. unclustered :
If order of data records is the same as order of index data entries, then called clustered index.
Index entries Dataentries
direct search for (Index File) (Data file) Data Records
data entries entries^ Data
Data Records
CLUSTERED UNCLUSTERED
Useful tool to speedup the data access
Can be unique or non-unique
Can be implemented through different techniques
Be careful; they involve overhead
Show the data to a users’ group that is necessary/required for them Give only necessary authorizations No concern with rest of the data
Efficiency
Part of a query that is frequently used (a subquery), define it as a view The view definition will be stored and will be executed anytime anywhere view is referred Docsity.com
Not exactly the external views of 3-level schema architecture Major Types Dynamic Materialized Partitioned Simple/complex