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Oracle – 5 – Iterative Processing with Loops

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Iterative processing with loops is a fundamental concept in Oracle’s PL/SQL programming language. Loops allow you to execute a block of code repeatedly until a specific condition is met or a certain number of iterations is reached. This is particularly useful for tasks that require processing large amounts of data, performing batch operations, or implementing repetitive tasks. Oracle provides several types of loops to facilitate iterative processing:

  1. LOOP-END LOOP:
    • The basic LOOP-END LOOP construct allows you to create an infinite loop. You can use this loop when you want to perform an action repeatedly until a specific condition inside the loop is met.
    DECLARE counter NUMBER := 0; BEGIN LOOP counter := counter + 1; EXIT WHEN counter > 5; -- Perform some repetitive action here END LOOP; END; In this example, the loop continues until the counter variable exceeds 5.
  2. FOR LOOP:
    • A FOR LOOP allows you to iterate over a specified range of values, such as a numeric range or a collection. It simplifies loop control by automatically incrementing or decrementing a loop counter.
    DECLARE -- Iterate from 1 to 5 BEGIN FOR i IN 1..5 LOOP -- Perform some repetitive action using 'i' END LOOP; END;
  3. WHILE LOOP:
    • A WHILE LOOP executes a block of code repeatedly as long as a specified condition is true. It’s useful when you need to loop based on a dynamic condition.
    DECLARE counter NUMBER := 0; BEGIN WHILE counter < 5 LOOP counter := counter + 1; -- Perform some repetitive action here END LOOP; END;
  4. EXIT and CONTINUE Statements:
    • Within loops, you can use the EXIT statement to terminate the loop prematurely when a particular condition is met. The CONTINUE statement allows you to skip the remaining code in the current iteration and move to the next iteration.
    DECLARE counter NUMBER := 0; BEGIN LOOP counter := counter + 1; IF counter = 3 THEN CONTINUE; -- Skip the rest of this iteration END IF; EXIT WHEN counter > 5; -- Perform some repetitive action here END LOOP; END;

Iterative processing with loops in Oracle PL/SQL is essential for tasks that require repetitive operations, such as processing records in a database table, calculating aggregates, or implementing complex business logic. By choosing the appropriate loop type and controlling loop conditions, you can efficiently handle a wide range of tasks in your database applications.