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Flashcards in Indexing Deck (11):

What is an index?

A data structure that allows for fast lookup for records in a file


Can an index allow records to be retrieved in sorted order?

Yes it can allow that


Describe a data file and and index file

Data File: the file that actually contains the records

Index File: The file that stores the index information


What is a Search Key

The set of attributes stored by the index to the find records in the data file


does the search key have to be unique?

NO it doesn't, more than one record may have the same search key value


What is an index entry?

One index record that contains a search key value and pointer to the location of the record with that value


What is the difference between ordered and unordered files?

Ordered files are sorted on the search key, unordered files are not


Dense vs Sparse indexes

A dense index has an index entry for every record in the data file

A sparse index has index entries for only some of the data file records


Primary (clustering) indexes vs Secondary indexes

A primary index sorts the data file by its search key. The search key doesn't have to be the same as the primary key

A 2NDary index doesn't determine the organization of the data file


Single-Level vs Multi-Level indexes

Single-level indexes have only one index level

multi-level indexes have several levels of indexes on the SAME FILE


Formula for sparse index based on key?