In SQL, the LAST_VALUE function is used to return the last value in a group of rows. It is part of the window function family and can be particularly useful when you want to find the last occurrence of a specific data point within a group or partition.

To use LAST_VALUE, you’ll need to specify the column you want to retrieve the last value from within the window frame. You also need to define the window frame using the OVER clause.

Let’s take a look at an example to better understand how to use LAST_VALUE:

SELECT product_id, order_date,
  LAST_VALUE(price) OVER (PARTITION BY product_id ORDER BY order_date
                          ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS last_price
FROM sales;

In this example, we have a table named sales with columns product_id, order_date, and price. We want to find the last price of each product within their respective order dates.

The OVER clause partitions the data by product_id and orders it by order_date. The ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING specifies the window frame as all rows within each partition.

The result set will include the product_id, order_date, and last_price columns. The last_price column will display the last price of each product within the defined window frame.

Remember to adapt the example code to your specific database schema and column names.

In summary, by utilizing the SQL LAST_VALUE function along with the OVER clause, you can easily retrieve the last value within a group of rows based on your specified criteria. This can be very useful when analyzing time-series data or tracking the latest data point for each category.

#SQL #WindowFunctions