NOT Operator
If you preface a condition with the keyword NOT, the test is TRUE
only
if the condition that NOT qualifies is FALSE
. If
the condition that NOT qualifies has a NULL or an UNKNOWN value, the
NOT operator has no effect.
The following truth table shows the effect of NOT with 3–valued
Boolean operands. Here T represents a
![begin figure description - This figure is described in the surrounding text - end figure description](sqls002.gif)
TRUE
condition,
F represents a FALSE
condition, and a question mark
(?
) represents an UNKNOWN
condition.
(An UNKNOWN
value can occur when an operand is NULL).
![begin figure description - This figure is described in the surrounding text - end figure description](sqls002.gif)
The left column shows the value of the operand of the NOT operator, and the right column shows the returned value after NOT is applied to the operand.