In this blog post, we will explore how to use the LAST_VALUE function in SQL along with the MINUS statement to get the last value from a column and perform calculations on it.

What is the LAST_VALUE function?

The LAST_VALUE function is a window function in SQL that returns the last value within a specified window frame. It is often used in combination with other functions like ROW_NUMBER or PARTITION BY to get the desired result.

Syntax of the LAST_VALUE function

The syntax of the LAST_VALUE function is as follows:

LAST_VALUE (expression) OVER (PARTITION BY partition_clause ORDER BY order_clause
                             ROWS BETWEEN frame_start AND frame_end)

Here, expression represents the column or expression from which you want to get the last value. partition_clause allows you to divide the result set into partitions, and order_clause specifies the order in which the rows should be evaluated.

Using SQL LAST_VALUE with MINUS statement

Let’s say we have a table called orders with the following data:

Now, suppose we want to find the difference between the last order amount and each order amount. We can achieve this using the LAST_VALUE function along with the MINUS statement.

Here is an example query that demonstrates this:

SELECT order_id, amount,
       LAST_VALUE(amount) OVER (ORDER BY order_id) - amount AS difference
FROM orders;

In this query, we use the LAST_VALUE function to get the last amount value in ascending order of order_id. We then subtract each amount value from the last value using the minus operator.

The result of the above query will be:

As you can see, the difference column shows the difference between each order amount and the last order amount.

Conclusion

The LAST_VALUE function in SQL provides a useful way to get the last value within a specified window frame. By combining it with the MINUS statement, you can perform calculations on the last value and achieve the desired result.