An index consists of one or more columns used to uniquely identify each row within a table. Operating as a SAS object containing the values in one or more columns in a table, an index is composed of one or more columns and may be defined as numeric, character, or a combination of both.
There is no rule that says a table has to have an index, but they can often make information retrieval more efficient and considerably faster.
For example, if you know a specific part number and its location from a list of thousands, then you can look up the part and find its manufacturer, cost, and location far more efficiently than if you did not know this information.
When defining an index, you should first understand ...