Clustered vs. Unclustered Index

• Suppose that the data records are stored in a Heap file.

  • To build clustered index, first sort the Heap file (with some free space on each page for future inserts).
  • Overflow pages may be needed for inserts. (Thus, order of data recs is `close to’, but not identical to, the sort order.)

Index entries

Data entries

direct search for

(Index File)

(Data file)

Data Records

data entries

Data entries

Data Records

CLUSTERED

UNCLUSTERED

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