In SQL, the LAST_VALUE function is used to retrieve the last value within a group of rows. It can be quite useful when working with ordered data and you need to access the last value based on certain criteria. In addition to using the LAST_VALUE function alone, you can also combine it with logical operators to further refine your query results.

Let’s say we have a table called sales with the following columns: product_name, date, quantity_sold. We want to find the last value of quantity_sold for each product where the quantity is greater than 100. We can use the LAST_VALUE function along with a logical operator to accomplish this.

Here’s an example query using the LAST_VALUE function with a logical operator:

SELECT product_name, 
       LAST_VALUE(quantity_sold) 
           OVER (PARTITION BY product_name ORDER BY date 
                 ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS last_quantity_sold
FROM sales
WHERE quantity_sold > 100;

In this query, we use the LAST_VALUE function within the windowing clause of the OVER keyword. The PARTITION BY clause ensures that the LAST_VALUE is calculated for each distinct product_name. Then, we order the rows by the date column. The ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING clause specifies that we want to consider all rows within the partition. Finally, in the WHERE clause, we specify the condition quantity_sold > 100 to filter out rows where the quantity is not greater than 100.

The result of this query will provide the last value of quantity_sold for each product where the quantity is greater than 100.

Conclusion

By combining the SQL LAST_VALUE function with logical operators, you can effectively filter and retrieve the last value based on specific conditions within your data. This allows for more precise and targeted result sets when working with ordered data.