Filter
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D
EFINING
F
ILTER
F
ORMULAS
7-9
Logical_Operator – Legal values include:
AND – Both expressions must be true to meet a given condition
OR – One true expression is enough to meet a given condition
Elements of Filter Formulas
Notes: 1. The equal to (==) and unequal (!=) expressions follow C language syntax.
2. If more than one expression is used to define a filter, first enclose each expression in parentheses and
then combine them with AND or OR. Parentheses are used to maintain the order of evaluation.
Otherwise conditions are evaluated from left to right.
3. If you want to test a log process without saving data into the database, set the filter formula to an
impossible condition; for example, (TIME<000000).
Table 7-2 Elements of Filter Formulas
Parameter Example Description
Variable VALUE Value of the data
Date when the value is reached
Time when the value is reached
Relation >
<
>=
==
!=
Greater than
Less than
Greater than or equal to
Less than or equal to
Not equal
Value 256
200040520
132201
Positive number (4 byte unsigned integer)
Date format (YYYYMMDD) for 20 March 2004
Time format (HHMMSS) for 01:55:01pm
Logical_Operator AND
OR
Both statements must be true
Either statement may be true