If no values in WHERE clauses match the result of the selector in the CASE clause, the sequence of statements in the ELSE clause executes. ... When the IF THEN statement has no ELSE clause and the condition is not met, PL/SQL does nothing instead raising an error.
Instead of having to write multiple pieces of code for different outcomes, you can use an elseif statement and make your code easier to read and easier to understand.
We use SQL Not Equal comparison operator (<>) to compare two expressions. For example, 10<>11 comparison operation uses SQL Not Equal operator (<>) between two expressions 10 and 11
