database-indexing

Question

How many different secondary indices are possible for a table with n attributes(Not necessarily at the same time)?

Comments

i think N

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nope this answer not given

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n! ???

Answer 1

you can choose any number of attributes out of remaining (n-1) attributes(assumed primary index is built using only single attribute) for secondary index. Hence 2^n-1

Comments

actually this isnot the answer given

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@resilient. Whats the answer given?

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Is the answer 1 ?

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how r u getting in the powers of 2, u mean we should  try to form secondary index on more than one attribute which will unnecessarily increase the size of index entries in the index table

I think it should be N-1 because we can form a secondary index on any key remaining(n-1) because 1 key is used for primary index, it is like this, when in a relation like emp_no is already unique and we have made already primary index on it but there is some need, we want to fetch some data based on emp_name than we can make a secondary index on it..