Loops are an essential part of programming as they allow you to repeat a block of code multiple times. In SQL Server, there are different types of loops that you can use to achieve this. In this article, we will explore the different types of loops in SQL Server and how to use them effectively.

While Loops

The while loop in SQL Server is used to repeat a block of code as long as a certain condition is true. The syntax for a while loop is as follows:

WHILE condition
BEGIN
    -- Code to be executed
END

Here’s an example of a while loop that calculates the factorial of a number:

DECLARE @n INT = 5;
DECLARE @result INT = 1;

WHILE @n > 1
BEGIN
    SET @result = @result * @n;
    SET @n = @n - 1;
END

SELECT @result AS Factorial;

This while loop calculates the factorial of 5 by multiplying the current result with the current value of n and then decrementing n by 1. The loop continues until n is greater than 1. The final result is then displayed.

For Loops

The for loop in SQL Server is used to iterate over a set of values. It is often used when you have a finite list of items that you want to process. The syntax for a for loop is as follows:

DECLARE @variable datatype;
DECLARE @list TABLE (value datatype);

-- Populate the list table with values

FOR @variable IN (SELECT value FROM @list)
BEGIN
    -- Code to be executed
END

Here’s an example of a for loop that iterates over a list of numbers:

DECLARE @numbers TABLE (number INT);
INSERT INTO @numbers VALUES (1), (2), (3), (4), (5);

DECLARE @sum INT = 0;

FOR @number IN (SELECT number FROM @numbers)
BEGIN
    SET @sum = @sum + @number;
END

SELECT @sum AS Sum;

This for loop calculates the sum of all the numbers in the list by adding each number to the current sum. The loop iterates over each number in the list and continues until all numbers have been processed. The final sum is then displayed.

Break, Continue, and Pass Statements

In addition to the basic loop constructs, SQL Server also provides three statements that can be used within loops to control the flow of execution:

• The BREAK statement is used to exit the loop immediately.
• The CONTINUE statement is used to skip the rest of the current iteration and move to the next iteration.
• The PASS statement is used as a placeholder and does nothing.

These statements can be useful in certain situations where you need to control the flow of execution within a loop.

Conclusion

Loops are powerful constructs in SQL Server that allow you to repeat a block of code multiple times. By understanding the different types of loops and how to use them effectively, you can write more efficient and flexible SQL scripts. Experiment with loops in SQL Server to see how they can enhance your programming skills.

Article Last Updated: 2022-03-25