SAS 9.4 Language Reference, 3rd Edition

Chapter 11

WHERE-Expression Processing

Definition of WHERE-Expression Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

Where to Use a WHERE Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

Syntax of WHERE Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

WHERE Expression Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

Specifying an Operand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

Specifying an Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

Combining Expressions By Using Logical Operators . . . . . . . . . . . . . . . . . . . . . . . 168

Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

Processing Compound Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Using Parentheses to Control Order of Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 169

Improving Performance of WHERE Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

Processing a Segment of Data That Is Conditionally Selected . . . . . . . . . . . . . . . . 170

Applying FIRSTOBS= and OBS= Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

Applying FIRSTOBS= and OBS= to a Subset of Data . . . . . . . . . . . . . . . . . . . . . 171

Processing a SAS View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Deciding Whether to Use a WHERE Expression or a Subsetting IF Statement . 173

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 that contains sales records, you might 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 can 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;

157