Search conditions can be used to choose a subset of the rows from a table in a FROM clause in a SELECT statement, or in expressions
such as an IF or CASE to select specific values. In UltraLite, every condition evaluates as one of three states: TRUE, FALSE,
or UNKNOWN. When combined, these states are referred to as three-valued logic. The result of a comparison is UNKNOWN if either value being compared is the NULL value. Search conditions are satisfied
only if the result of the condition is TRUE.
AND
The combined condition is TRUE if both conditions are TRUE, FALSE if either condition is FALSE, and UNKNOWN otherwise.
condition1ANDcondition2
OR
The combined condition is TRUE if either condition is TRUE, FALSE if both conditions are FALSE, and UNKNOWN otherwise.
NOT
The NOT condition is TRUE if condition is FALSE, FALSE if condition is TRUE, and UNKNOWN if condition is UNKNOWN.
IS
The condition is TRUE if the expression evaluates to the supplied truth-value, which must be one of TRUE, FALSE, or UNKNOWN. Otherwise, the value is FALSE.
The IS NULL condition is satisfied if the column contains a NULL value. If you use the IS NOT NULL operator, the condition
is satisfied when the column contains a value that is not NULL. This example shows an IS NULL condition: WHERE paid_date IS
NULL.
Syntax 1