11.5. Logical Operators

PL/SQL supports a full set of logical operators that may be used for logical and arithmetic expressions. The operations defined on DATE type allow manipulation and comparison of DATE type variables. Use “IS NULL” and “NOT NULL” in comparison statements if any of the values may be NULL. The following is a summary of comparison operators.

 =    is equal to                   IF (a = b)  THEN
!=    is not equal to               IF (a != b) THEN
<>    is not equal to               IF (a <> b) THEN
>     is greater than               IF (a = b)  THEN
>=    is greater than or equal to   IF (a != b) THEN
<     is less than                  IF (a <> b) THEN
<=    is less than or equal to      IF (a != b) THEN

The following function returns TRUE if the DATE parameter passed is yesterday.

 FUNCTION is_yesterday (v_date in DATE) RETURN ...

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