SAS 9.4 Language Reference, 6th Edition

MIN and MAX Operators

Use the MIN or MAX operators to find the minimum or maximum value of two

quantities. Surround the operators with the two quantities whose minimum or maximum

value you want to know.

• The MIN operator returns the lower of the two values.

• The MAX operator returns the higher of two values.

For example, if A is less than B, then the following would return the value of A:

where x = (a min b);

Note: The symbol representation >< is not supported, and <> is interpreted as “not equal

to.”

Concatenation Operator

The concatenation operator concatenates character values. You indicate the

concatenation operator as follows:

• || (two OR symbols)

• !! (two exclamation marks)

• ¦¦ (two broken vertical bars).

For example:

where name = 'John'||'Smith';

Prefix Operators

The plus sign (+) and minus sign (–) can be either prefix operators or arithmetic

operators. They are prefix operators when they appear at the beginning of an expression

or immediately preceding an open parenthesis. A prefix operator is applied to the

variable, constant, SAS function, or parenthetic expression.

where z = −(x + y);

Note: The NOT operator is also considered a prefix operator.

Combining Expressions By Using Logical

Operators

Syntax

You can combine or modify WHERE expressions by using the logical operators (also

called Boolean operators) AND, OR, and NOT. The basic syntax of a compound

WHERE expression is as follows:

WHERE where-expression-1 AND | OR | NOT where-expression-n

AND combines two conditions by finding observations that satisfy both conditions. For

example:

where skill eq 'java' and years eq 4;

OR combines two conditions by finding observations that satisfy either condition or

both. For example:

188 Chapter 11 • WHERE-Expression Processing

where skill eq 'java' or years eq 4;

NOT modifies a condition by finding the complement of the specified criteria. You can

use the NOT logical operator in combination with any SAS and WHERE expression

operator. And you can combine the NOT operator with AND and OR. For example:

where skill not eq 'java' or years not eq 4;

The logical operators and their equivalent symbols are shown in the following table:

Table 11.4 Logical (Boolean) Operators

Symbol Mnemonic Equivalent

& AND

! or | or ¦ OR

^ or ~ or ¬ NOT

Processing Compound Expressions

When SAS encounters a compound WHERE expression (multiple conditions), the

software follows rules to determine the order in which to evaluate each expression.

When WHERE expressions are combined, SAS processes the conditions in a specific

order:

1. The NOT expression is processed first.

2. Then the expressions joined by AND are processed.

3. Finally, the expressions joined by OR are processed.

Using Parentheses to Control Order of Evaluation

Even though SAS evaluates logical operators in a specific order, you can control the

order of evaluation by nesting expressions in parentheses. That is, an expression

enclosed in parentheses is processed before one not enclosed. The expression within the

innermost set of parentheses is processed first, followed by the next deepest, moving

outward until all parentheses have been processed.

For example, suppose you want a list of all the Canadian sites that have both

SAS/GRAPH and SAS/STAT software, so you issue the following expression:

where product='GRAPH' or product='STAT' and country='Canada';

The result, however, includes all sites that license SAS/GRAPH software along with the

Canadian sites that license SAS/STAT software. To obtain the correct results, you can

use parentheses, which causes SAS to evaluate the comparisons within the parentheses

first, providing a list of sites with either product licenses, then the result is used for the

remaining condition:

where (product='GRAPH' or product='STAT') and country='Canada';

Combining Expressions By Using Logical Operators 189