LOOPs in Oracle

Oracle PL/SQL offers several loop constructs to iterate over a set of statements or perform repetitive tasks. Here's an overview of the main types of loops in Oracle PL/SQL along with examples:

1. WHILE Loop:

   The WHILE loop executes a sequence of statements repeatedly as long as a condition is true.

   DECLARE

       counter NUMBER := 1;

   BEGIN

       WHILE counter <= 5 LOOP

           DBMS_OUTPUT.PUT_LINE('Counter: ' || counter);

           counter := counter + 1;

       END LOOP;

   END;

   /

2. FOR Loop:

   The FOR loop iterates over a range of integers or a collection of elements.

   - Numeric FOR Loop:

   

     DECLARE

         i NUMBER;

     BEGIN

         FOR i IN 1..5 LOOP

             DBMS_OUTPUT.PUT_LINE('Counter: ' || i);

         END LOOP;

     END;

     /

   - Cursor FOR Loop (Looping through query result):

     DECLARE

         v_name employees.first_name%TYPE;

     BEGIN

         FOR emp_rec IN (SELECT first_name FROM employees) LOOP

             v_name := emp_rec.first_name;

             DBMS_OUTPUT.PUT_LINE('Name: ' || v_name);

         END LOOP;

     END;

     /

3. LOOP-END LOOP:

   The LOOP-END LOOP construct allows indefinite looping until an exit condition is met using the EXIT statement.

   DECLARE

       counter NUMBER := 1;

   BEGIN

       LOOP

           EXIT WHEN counter > 5;

           DBMS_OUTPUT.PUT_LINE('Counter: ' || counter);

           counter := counter + 1;

       END LOOP;

   END;

   /

4. Nested Loops:

   You can nest loops within each other to perform more complex iterations.

   DECLARE

       i NUMBER;

       j NUMBER;

   BEGIN

       FOR i IN 1..3 LOOP

           FOR j IN 1..2 LOOP

               DBMS_OUTPUT.PUT_LINE('i: ' || i || ', j: ' || j);

           END LOOP;

       END LOOP;

   END;

   /

These examples demonstrate how to use different types of loops in Oracle PL/SQL. They can be useful for various tasks such as iterating over collections, processing query results, or performing repetitive operations.

Here are five frequently asked questions (FAQs) about loops in Oracle PL/SQL:-

1. What is the difference between a WHILE loop and a FOR loop in Oracle PL/SQL?

   - A WHILE loop is used when the number of iterations is not known beforehand, and it continues to execute as long as a specified condition is true.

   - A FOR loop is used when the number of iterations is known beforehand, either as a range of integers or as a collection, and it iterates over the specified range or collection.

2. How do I exit a loop prematurely in Oracle PL/SQL?

   - You can exit a loop prematurely using the EXIT statement. This statement is typically placed within the loop body and is followed by a condition that determines when the loop should be exited.

3. Can I nest loops within each other in Oracle PL/SQL?

   - Yes, you can nest loops within each other in Oracle PL/SQL. This allows you to perform more complex iterations, such as iterating over a two-dimensional array or processing hierarchical data structures.

4. What is the purpose of the LOOP-END LOOP construct in Oracle PL/SQL?

   - The LOOP-END LOOP construct in Oracle PL/SQL allows you to create an indefinite loop that continues executing until an exit condition is met. This type of loop is useful when the number of iterations is not known beforehand.

5. How do I handle exceptions inside a loop in Oracle PL/SQL?

   - You can use exception handling constructs such as EXCEPTION blocks inside a loop to handle errors that occur during loop execution. This allows you to gracefully handle exceptions and continue loop execution or take appropriate actions based on the exception type.