Chapter 12: WHERE-Expression Processing

Definition of WHERE-Expression Processing

WHERE-expression processing		enables you to conditionally select a subset of observations, so that SAS processes only the observations that meet a set of specified conditions. For example, if you have a SAS data set containing sales records, you may want to print just the subset of observations for which the sales are greater than $300,000 but less than $600,000. In addition, WHERE-expression processing may improve efficiency of a request. For example, if a WHERE expression can be optimized with an index, it is not necessary for SAS to read all observations in the data set in order to perform the request.
WHERE expression		defines a condition that selected observations must satisfy in order to be processed . You can have a single WHERE expression, referred to as a simple expression , such as the following: where sales gt 600000; Or you can have multiple WHERE expressions, referred to as a compound expression , such as the following: where sales gt 600000 and salary lt 100000;