9 state nine rules of thumb for choosing indexes ans

9. State nine rules of thumb for choosing indexes.

Chapter 5 Questions & Answer
5. use an index when there is significant variety in the values of an attribute.
6. Before creating an index on a field with long values, consider first creating a compressed
version of the values and then indexing on the coded version.
7. If the key for the index is going to be used for determining the location where the record
will be stored, then the key for this index should be a surrogate key so that the values cause
records to be evenly spread across the storage space.
8. Check your DBMS for a limit, if any, on the number of indexes allowable per table.
9. Be careful of indexing attributes that have null values.
10. Explain why an index is useful only if there is sufficient variety in the values of an attribute.