When working with SQL, the LAST_VALUE function can be very useful for retrieving the last value in a sequence of rows. In addition to simply returning the last value, the LAST_VALUE function can also work in conjunction with comparison operators to further refine your query results.

Here’s an example to demonstrate the usage of LAST_VALUE with comparison operators in SQL:

SELECT product_id, product_name, price,
    LAST_VALUE(price) OVER(PARTITION BY product_id ORDER BY sale_date ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS last_price
FROM sales_data
WHERE price > LAST_VALUE(price) OVER(PARTITION BY product_id ORDER BY sale_date ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING);

In this example, we have a table called “sales_data” with columns for product_id, product_name, price, and sale_date. We want to retrieve the last recorded price for each product, but only for the rows where the current price is greater than the previous price.

To achieve this, we use the LAST_VALUE function along with the comparison operators in the WHERE clause. The PARTITION BY clause groups the rows by product_id, and the ORDER BY clause sorts the rows by sale_date. This ensures that the last_value function will return the last price for each product.

The ROWS clause specifies the window frame for sorting the rows. In our example, we use “ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING” to consider only the rows up to the previous row. This allows us to compare the current price with the previous price.

The result of this query will be a list of product records that meet the condition where the current price is greater than the previous price.

Using LAST_VALUE with comparison operators can be a powerful way to filter your query results based on the last value in a sequence of rows. It allows you to refine your queries and retrieve only the relevant data you need.