Indexes
A 1-d index is based on the value of a single attribute A.
Some possible properties of A:
- may be used to sort data file
(or may be sorted on some other field)
- values may be unique
(or there may be multiple instances)
Taxonomy of index types, based on properties of index attribute:
| primary |
| index on unique field, may be sorted on A |
| clustering |
| index on non-unique field, file sorted on A |
| secondary |
| file not sorted on A |
A given table may have indexes on several attributes.
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