Progress
SQL-89
Guide and Reference
Logical Expressions
Logical expressions are expressions that evaluate to TRUE, FALSE, or UNKNOWN (equivalent to the Progress unknown value and to the Progress/SQL null value). You combine logical expressions with the logical operators AND and OR, and you negate a logical expression by prepending the logical operator NOT. The resulting logical expression has the value TRUE, FALSE, or UNKNOWN.
If you combine two logical expressions using AND, determine the truth value of the result from Table 2–2.
Table 2–2: Truth Table for AND AND TRUE UNKNOWN FALSE TRUE TRUE UNKNOWN FALSE UNKNOWN UNKNOWN UNKNOWN FALSE FALSE FALSE FALSE FALSE
If you combine two logical expressions using OR, determine the truth value of the result from Table 2–3.
Table 2–3: Truth Table for OR OR TRUE UNKNOWN FALSE TRUE TRUE TRUE TRUE UNKNOWN TRUE UNKNOWN UNKNOWN FALSE TRUE UNKNOWN FALSE
If you prepend NOT to a logical expression, determine the truth value of the result from Table 2–4.
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