a. Briefly explain the three main alternatives for storing information in a data entry of an index. b. Define clustered index, and discuss the relation between the three alternatives and clustered/unclustered indexes.
Ans a. The three main alternatives for storing information in a data entry of an index are: - The first alternative can be a data entry k* which is an actual data record with search key value k.
- The second alternative is a data record that is a {k,rid} pair where rid is actually the record id of a data record with search key value k.
- The third alternative is a data record that is a {k,rid-list} pair where rid-list is actually list of record ids of a data records with search key value k.
Ans b. Clustered Index: "A clustered index is a type of index where the table records are re-ordered physically to match the index. So, the tables data can only be sorted in one way. Therefore,there can only be one clustered index in one particular table." If the index contains data records as "data entries" that means the index is using alternative one. Alternative one is generally clustered while the alternative 2 and 3 are generally unclustered.
| 
