self_doubt

Question

I am confused about indexing being densed or sparse, Read a lot of answer but can’t figure out

1. Primary Index is always sparse : since indexing is done of key attribute and records(files) are ordered so we create index only for anchor of the block(group of records).
2. Secondary index is dense : Since indexing is done on the basis of Non-key/key attribute and records are un-ordered.
3. Clustering indexing can be sparse or dense: Sparse when we create index for Distinct non-key attributes attributes and there are multiple records having same non-key attributes and Dense when there is unique record with non-key attribute.
4. B- tree indexing is Dense ; since we have and indexing for every key attribute.
5. B+ tree is Sparse since indexing is not for every record and is only for some records.

Please correct me If I am wrong at some point and If I am right then please comment.

Comments

Brother @balchandar reddy san I agree what you said about secondary indexing, But I think that clustered index can be both dense and Sparse for the reason I mentioned above.

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Dense when there is unique record with non-key attribute, not sure about this.

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i think 4 and 5 are wrong 

b and b+ can be dense or sparse depends on the file if is sorted or not.

if it is sorted then indexing can be done on blocks making it sparse

if it is unsorted then every record have to be in leaf node making it dense