Relational operators specify the relationship of value
expressions and perform the following kinds of operations:
o Compare a value with a range
o Match a pattern
o Test for missing fields
1 – Description
CDO uses mathematical relational operators and pattern testing
relational operators in its conditional expressions.
Mathematical relational operators are symbols that allow you
to compare values. Pattern testing relational operators are
keywords that allow you to test for a pattern of values. Unlike
the mathematical relational operators, each pattern testing
relational operator has its own unique syntax.
Pattern Testing Relational Operators lists the pattern testing
relational operators.
Table 5-6 Pattern Testing Relational Operators
Clause Relational Operation
BETWEEN True if the first value expression is less than or
equal to the second value expression and greater
than or equal to the third value expression.
CONTAINING True if the string specified by the second string
expression is found within the string specified
by the first string expression. CONTAINING is not
case sensitive.
MATCHING True if the second value expression matches a
substring of the first value expression. MATCHING
is not case sensitive. It uses the following
wildcard characters:
o Asterisk (*)- Matches any string of zero or
more characters
o Percent sign (%)-Matches any single character
in that position
STARTING True if the first characters of the first string
WITH expression match the second string expression.
STARTING WITH is case sensitive.
The logical operators AND, OR, and NOT let you compare two or
more conditional expressions and optionally reverse the value of
a conditional expression. The result of using a logical operator
is another conditional expression.
Mathematical Relational Operators lists the mathematical
relational operators. These operators allow you to compare
values. In all cases, if either value expression in a conditional
expression is null, the value of the entire condition is null.
Table 5-7 Mathematical Relational Operators
Permitted
Symbols Relational Operation
EQ or = True if the two value expressions are equal.
NE or <> True if the two value expressions are not equal.
GT or > True if the first value expression is greater than the
second.
GE or >= True if the first value expression is greater than or
equal to the second.
LT or < True if the first value expression is less than the
second.
LE or <= True if the first value expression is less than or
equal to the second.
Use either the alphabetic symbol or the mathematical symbol
from the Permitted Symbols column, but do not use both when you
specify a relational operator.
See the documentation for the languages and products that use
the repository to determine how that product evaluates character
string literals. In some cases, character string literals are
compared according to the ASCII collating sequence. Under ASCII,
lowercase letters have a greater value than uppercase letters,
and the letters near the beginning of the alphabet have a lesser
value than those near the end.
For products that compare character string literals according to
the ASCII collating sequence, the following statements are true:
o a > A
o a < z
o A < Z
To determine how CDO conditional expressions linked by logical
operators are evaluated, see the documentation for the product
that will be evaluating the conditional expression.
See the documentation for languages and products that use the
repository to determine how they evaluate character string
literals.
CAUTION
The NOT operator applies to conditional expressions. Do not
use the NOT operator and an equal sign instead of the NE
or <> relational operators. The following statement is not
valid:
WITH SALARY_AMOUNT IN S NOT = 30000
Use one of the following alternatives:
WITH NOT (SALARY_AMOUNT IN S = 30000)
WITH SALARY_AMOUNT IN S NE 30000
WITH SALARY_AMOUNT IN S <> 30000
2 – Examples
1.LAST_NAME CONTAINING "ith"
LAST_NAME NOT CONTAINING "son"
In this example, if LAST_NAME has the string ith, CDO evaluates
the CONTAINING clause as true; if LAST_NAME does not contain
the string son, CDO evaluates the CONTAINING clause as true.
2.SALARY_AMOUNT IN SH > 50000
In this example, the conditional expression is true if the
value in the SALARY_AMOUNT field is greater than 50,000.
3.NOT SALARY_AMOUNT IN SH < 50000
In this example, the conditional expression is true if the
value in the SALARY_AMOUNT field is less than 50,000.
4.DEFINE FIELD SEX
VALID IF (SEX CASE_SENSITIVE EQ "M") OR (SEX CASE_SENSITIVE EQ "F").
In this example, the DEFINE FIELD uses a case sensitive
relational operator in the VALID IF clause to test whether the
code to be entered in the field SEX is M or F. The conditional
expression is true if the value for the field SEX is M or F
(not m or f).
5.LAST_NAME MATCHING "*ON"
In this example, the conditional expression is true if the
field LAST_NAME has ON as the last two letters. You can use
this expression to find all records with LAST_NAME fields
satisfying this condition.
6.LAST_NAME IN FULL_NAME IN E MISSING
In this example, the conditional expression is true if the
LAST_NAME field in the FULL_NAME record of the EMPLOYEES
relation is missing.
7.LAST_NAME IN FULL_NAME IN E ALPHABETIC
In this example, CDO evaluates the field expression as true
when the LAST_NAME field from the FULL_NAME record of the
EMPLOYEES relation is alphabetic.
8.SALARY_AMOUNT NOT MISSING
In this example, the conditional expression is true if the
SALARY_AMOUNT field has a value that is not null.
9.SALARY_AMOUNT MATCHING "4*"
This example shows the matching clause used with numeric data
types. In this example, the matching clause finds all the
salaries that start with the number 4.
10SALARY_AMOUNT BETWEEN 40000 AND 49999
This example finds all salaries in a range by using the BETWEEN
clause.