The database commonly uses an index range scan to access selective data. The selectivity is the percentage of rows in the table that the query selects, with 0 meaning no rows and 1 meaning all rows. Selectivity is tied to a query predicate, such as WHERE last_name LIKE 'A%', or a combination of predicates.
Types of Distribution: Intensive, Selective and Exclusive Distribution. Some of the important types of distribution in international market are 1. Intensive 2. Selective and 3. Exclusive distribution.
For skewed distributions, it is quite common to have one tail of the distribution considerably longer or drawn out relative to the other tail. A skewed right distribution is one in which the tail is on the right side. A skewed left distribution is one in which the tail is on the left side.