Conditional Statement

Conditional selection statements, which run different statements for different data values.

The conditional selection statements are IF and and CASE.

The IF THEN statement has this structure:

IF condition THEN
  statements
END IF;
If the condition is true, the statements run; otherwise,
the IF statement does nothing. (For complete syntax, see "IF Statement".)

DECLARE
  grade CHAR(1);
BEGIN
  grade := 'B';

  IF grade = 'A' THEN
    DBMS_OUTPUT.PUT_LINE('Excellent');
  ELSIF grade = 'B' THEN
    DBMS_OUTPUT.PUT_LINE('Very Good');
  ELSIF grade = 'C' THEN
    DBMS_OUTPUT.PUT_LINE('Good');
  ELSIF grade = 'D' THEN
    DBMS_OUTPUT. PUT_LINE('Fair');
  ELSIF grade = 'F' THEN
    DBMS_OUTPUT.PUT_LINE('Poor');
  ELSE
    DBMS_OUTPUT.PUT_LINE('No such grade');
  END IF;
END;
/


OutPut:-

Very Good
PL/SQL procedure successfully completed.


case statement 


The case statement selects from sequence of conditions,and runs the corresponding statement.
it is simple & which evaluates a single expression & compares with several potential values.

The simple CASE statement has this structure:

CASE selector
WHEN selector_value_1 THEN statements_1
WHEN selector_value_2 THEN statements_2
...
WHEN selector_value_n THEN statements_n
[ ELSE
  else_statements ]
END CASE;]

Else clause is an optional if you do not specify an else clause and none of the result of the case

expression oracle  will raise an a case not found error.

The following is an example of a simple case statement that uses the grade type for selecting apprisal

of an candidate

DECLARE
  grade CHAR(1);
BEGIN
  grade := 'B';

  IF grade = 'A' THEN
    DBMS_OUTPUT.PUT_LINE('Excellent');
  ELSIF grade = 'B' THEN
    DBMS_OUTPUT.PUT_LINE('Very Good');
  ELSIF grade = 'C' THEN
    DBMS_OUTPUT.PUT_LINE('Good');
  ELSIF grade = 'D' THEN
    DBMS_OUTPUT. PUT_LINE('Fair');
  ELSIF grade = 'F' THEN
    DBMS_OUTPUT.PUT_LINE('Poor');
  ELSE
    DBMS_OUTPUT.PUT_LINE('No such grade');
  END IF;
END;

Output:

Very Good


LOOP Statements

Loop statements run the same statements with a series of different values. The loop statements are:

Basic LOOP
FOR LOOP
Cursor FOR LOOP
WHILE LOOP
The statements that exit a loop are:

EXIT
EXIT WHEN
The statements that exit the current iteration of a loop are:

CONTINUE
CONTINUE WHEN




EXIT WHEN Statement

The EXIT WHEN statement exits the current iteration of a loop when the condition in its WHEN clause is true, and transfers control to the end of either the current loop or an enclosing labeled loop.

Each time control reaches the EXIT WHEN statement, the condition in its WHEN clause is evaluated. If the condition is not true, the EXIT WHEN statement does nothing. To prevent an infinite loop, a statement inside the loop must make the condition true, as in Example 4-10.

In Example 4-10, the EXIT WHEN statement inside the basic LOOP statement transfers control to the end of the current loop when x is greater than 3. Example 4-10 is logically equivalent to Example 4-9.

Example 4-10 Basic LOOP Statement with EXIT WHEN Statement

DECLARE
  x NUMBER := 0;
BEGIN
  LOOP
    DBMS_OUTPUT.PUT_LINE('Inside loop:  x = ' || TO_CHAR(x));
    x := x + 1;  -- prevents infinite loop
    EXIT WHEN x > 3;
  END LOOP;
  -- After EXIT statement, control resumes here
  DBMS_OUTPUT.PUT_LINE('After loop:  x = ' || TO_CHAR(x));
END;
/