Yes, its Duplicate but I still asked due to no satisfactory answer.
which statement is true?
1)For any data file it is possible to construct two separate sparse first level index on different keys.
2)For any data file it is possible to construct two separate dense first level index on different keys.
3)For any data file it is possible to construct a sparse first level index and a dense second level index both should be useful
4) none.
From which topic/resource this concept can be cleared.