Database Indices

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What happens when an entry for the search key exists in a sparse index?

The entry is left unchanged.

The entry is replaced with the previous search-key value in the file.

The entry is deleted by replacing it with the next search-key value in the file. (correct)

The entry is inserted into the index.

In a dense index, what happens when the search-key value does not appear in the index?

The search-key value is deleted from the index.

The search-key value is inserted into the index. (correct)

The index is reorganized.

The index is left unchanged.

What is the purpose of a hash function in file organization?

To sort the records in a file.

To optimize query performance.

To reorganize the index periodically.

To obtain the bucket of a record directly from its search-key value. (correct)

What problem arises when the number of buckets (B) is small in a hash file structure?

Too many overflows occur. Signup and view all the answers

What is the purpose of periodic re-organization of the file with a new hash function?

To solve the problem of too many overflows. Signup and view all the answers

What is the benefit of dynamically modified hash functions?

Adaptability to changing data distributions. Signup and view all the answers

What is the primary purpose of an index structure in a database?

To enable fast random access to specific data items Signup and view all the answers

What is the term for the attribute or set of attributes used to look up records in a file?

Search key Signup and view all the answers

What type of search is supported efficiently by certain indexing techniques?

Range search Signup and view all the answers

What is the term for the time taken to find a particular data item or set of items?

Access time Signup and view all the answers

What is the purpose of a primary index in a file?

To specify the sequential order of the file Signup and view all the answers

What search technique is used to search through the indices of the index file?

Binary search Signup and view all the answers

What is the primary reason why a nested-loop join is considered expensive?

It requires examination of every pair of tuples in the two relations Signup and view all the answers

What happens when at least one relation fits into memory?

The relation that fits into memory is made the inner relation Signup and view all the answers

What is the primary function of an index in a database?

To speed up access to the desired data Signup and view all the answers

What is the key difference between an ordered index and a hash index?

Ordered indices have search keys in sorted order, while hash indices use a hash function Signup and view all the answers

What is the purpose of a search key in an index?

To locate records directly in a file Signup and view all the answers

What is the benefit of using an index in a database?

It speeds up access to the desired data Signup and view all the answers

Database Indices

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