When working with cursor-based SQL operations, it often becomes necessary to handle conditional logic using the CASE and WHEN statements. These statements allow us to evaluate conditions and perform different actions based on the results. In this blog post, we will explore how to handle CASE and WHEN statements in cursor-based SQL operations.

What are CASE and WHEN statements?

The CASE statement in SQL allows us to perform conditional logic within our queries. It evaluates a series of conditions and returns a result based on the first condition that is true.

The WHEN statement is used within the CASE statement to define the conditions and corresponding actions. It allows us to specify different scenarios and determine the appropriate action for each scenario.

Using CASE and WHEN statements with cursors

Cursors are a powerful tool for performing operations on a set of rows returned by a query. They allow us to iterate through the result set and perform actions for each row.

When working with cursors, we can include CASE and WHEN statements to handle conditional logic for each row. Here’s an example:

DECLARE cur CURSOR FOR
SELECT customer_name, age
FROM customers
WHERE age > 18;

DECLARE @customer_name VARCHAR(50);
DECLARE @age INT;

OPEN cur;
FETCH NEXT FROM cur INTO @customer_name, @age;

WHILE @@FETCH_STATUS = 0
BEGIN
    CASE
        WHEN @age <= 25 THEN
            PRINT 'Customer ' + @customer_name + ' is a young adult.';
        WHEN @age <= 50 THEN
            PRINT 'Customer ' + @customer_name + ' is in middle age.';
        ELSE
            PRINT 'Customer ' + @customer_name + ' is a senior citizen.';
    END;

    FETCH NEXT FROM cur INTO @customer_name, @age;
END;

CLOSE cur;
DEALLOCATE cur;

In this example, we declare a cursor that selects the customer_name and age columns from the customers table, filtering for customers over 18 years old. We then initialize variables to hold the values of these columns.

Inside the cursor loop, we use a CASE statement to evaluate the value of @age and print a message based on the age range. The WHEN statements define the conditions and corresponding actions for each age range.

Conclusion

Handling CASE and WHEN statements in cursor-based SQL operations allows us to incorporate conditional logic into our queries. By using these statements, we can perform different actions based on specific conditions for each row in a result set. This helps us to create more dynamic and flexible data manipulations with cursor-based SQL operations.

#cursor #SQL