Indexes can be unique or nonunique. Unique indexes guarantee that no two rows of a table have duplicate values in the key column or columns. For example, no two employees can have the same employee ID. Thus, in a unique index, one rowid exists for each data value. The data in the leaf blocks is sorted only by key.
Energy exists in many different forms. Examples of these are: light energy, heat energy, mechanical energy, gravitational energy, electrical energy, sound energy, chemical energy, nuclear or atomic energy and so on. These forms of energy can be transferred and transformed between one another.
In the universe there are kinds of energy and different ways it manifests itself. One common form is radiation. Radiation is the wave energy produced by electromagnetic forces. There are different kinds and their strength can be divided into three categories. There are alpha rays, beta rays, and finally gamma rays. Essentially each example is high energy particles traveling in a straight line.