Rockwell Automation FactoryTalk View Site Edition Users Guide - Manual (Page 553)

20 • C REATING EXPRESSIONS
20–7
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Relational operators
Relational operators compare two numeric or string values, to provide a true or false
result. If the statement is true, the expression returns a value of 1. If the statement is false,
the expression returns a value of 0.
The following table describes the relational operators, with examples. (For the numeric
examples, tag1 = 5 and tag2 = 7. For the string examples, serial_no = ST009.)
How string operands are evaluated
String operands are evaluated by case and by alphabetical order. Lower case letters are
greater than upper case letters. For example, h is greater than H. Letters later in the
alphabet are greater than those earlier in the alphabet. For example, B is greater than A.
Logical operators
Logical operators determine the validity of one or more statements. There are three logical
operators: AND, OR, and NOT. If the expression is true, the operators return a non-zero
value. If the expression is false, the operators return 0.
The following table describes the logical operators, with examples. (In the examples,
tag1 = 5 and tag2 = 7.)
Symbol Operator Numeric examples String examples
EQ, == equal tag1==tag2
false serial_no==“ST011”
false
NE, <> not equal tag1<>tag2
true serial_no<>“ST011”
true
LT, < less than tag1true serial_no<“ST011”
true
GT, > greater than tag1>tag2
false serial_no>“ST011”
false
LE, <= less than or equal to tag1<=tag2
true serial_no<=“ST011”
true
GE, >= greater than or equal to tag1>=tag2
false serial_no>=“ST011”
false
Symbols Operator Action Example
AND, && and If the statements to the right and to the left
of the operator are both true, returns a 1. (tag1Both statements are true; returns a 1.