DB Index

最新推荐文章于 2025-06-22 16:34:29 发布

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最新推荐文章于 2025-06-22 16:34:29 发布

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分类专栏： DB 文章标签： arrays performance table database each

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Clustered Index



Clustered Index :-

1.There can be only one Clustered index for a table

2.usually made on the primary key

3.the logical order of the index matches the physical stored

order of the rows on disk



Non-Clustered Index

1.There can be only 249 Clustered index for a table

2.usually made on the any key

3.the logical order of the index does not match the physical

stored order of the rows on disk

Bitmap index

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A bitmap index is a special kind of database index that uses bitmaps .

Bitmap indexes have traditionally been considered to work well for data such as gender, which has a small number of distinct values, e.g., male and female, but many occurrences of those values. This would happen if, for example, you had gender data for each resident in a city. Bitmap indexes have a significant space and performance advantage over other structures for such data. However, some researchers argue that Bitmap indexes are also useful for unique valued data which is not updated frequently.^[1] Bitmap indexes use bit arrays (commonly called "bitmaps") and answer queries by performing bitwise logical operations on these bitmaps