In SQL, the LAST_VALUE function is commonly used to retrieve the last value in a set of ordered rows. It can be particularly useful when combined with a CASE statement to conditionally select the last value based on certain criteria.

Here’s an example scenario: suppose we have a table called “products” that stores information about different products. Each product has a name and a category, and we want to retrieve the last product name for each category.

SELECT 
    category,
    LAST_VALUE(
        CASE
            WHEN category = 'Electronics' THEN name
            WHEN category = 'Clothing' THEN name
            ELSE NULL
        END
    ) OVER (PARTITION BY category ORDER BY id) AS last_product_name
FROM 
    products;

In the above example, we use the CASE statement inside the LAST_VALUE function to only select the name when the category matches either ‘Electronics’ or ‘Clothing’. For other categories, we return NULL. The PARTITION BY clause is used to reset the calculation of the last value for each category, while the ORDER BY clause specifies the order in which the rows should be evaluated.

By executing the above query, we can retrieve the last product name for each category based on our specified conditions. This can be helpful in various cases, such as finding the latest version of a product in a software release history or identifying the most recent sale in different regions.

In conclusion, the LAST_VALUE function combined with a CASE statement provides a powerful tool for retrieving the last value based on conditional logic in SQL queries. It can be especially useful when working with ordered data sets and when you need to retrieve specific values based on certain criteria.

#sql #lastvalue #casetatement