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.
A skewed (non-symmetric) distribution is a distribution in which there is no such mirror-imaging. 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. The above histogram is for a distribution that is skewed right. Skewed distributions bring a certain philosophical complexity to the very process of estimating a typical value for the distribution.