SAS 9.4 Language Reference, 6th Edition

Chapter 11

WHERE-Expression Processing

Definition of WHERE-Expression Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Where to Use a WHERE Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

Syntax of WHERE Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

WHERE Expression Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Specifying an Operand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Specifying an Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Combining Expressions By Using Logical Operators . . . . . . . . . . . . . . . . . . . . . . . 188

Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Processing Compound Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

Using Parentheses to Control Order of Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 189

Improving Performance of WHERE Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

Processing a Segment of Data That Is Conditionally Selected . . . . . . . . . . . . . . . . 190

Applying FIRSTOBS= and OBS= Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

Applying FIRSTOBS= and OBS= to a Subset of Data . . . . . . . . . . . . . . . . . . . . . 191

Processing a SAS View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Deciding Whether to Use a WHERE Expression or a Subsetting IF Statement . 193

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;

177