What is the difference between a primary index and a
secondary index? What is a duplicate data entry in an index?
Can a primary index contain duplicates?
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Answer Posted / khadija
1.A primary index is an index on a set of fields that includes the unique primary key for the field and is guaranteed not to contain duplicates. A Secondary index is an index that is not a primary index and may have duplicates.
2.Example,
Employee ID can be Example of it. Example,
Employee name can be example of it. Because Employee name can have similar values.
3.The primary index contains the key fields of the table. The primary index is automatically created in the database when the table is activated. If a large table is frequently accessed such that it is not possible to apply primary index sorting, you should create secondary indexes for the table.
4.The index in which the sort order of a search key is similar
to the sort order of a relation then the index is called
primary index. Ex, front index of the book. While in secondary index the order of the search key is in
different order from the order of the key in file. Ex, index
in back side of some book.
5.In the case of
Primary Index both keys and addresses of the records are
kept in order to search a particular record faster. In the case of Secondary Index only the addresses of the
records are kept in the index not the key.
6.There can be only one primary index. There can be many secondary indices.
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