In SQL, the LAST_VALUE function can be used to extract the last value in a column within a window of rows defined by an ORDER BY clause. This can be particularly useful with numeric functions to calculate running totals, find the maximum or minimum value in a window, or track changes in values over time.

Let’s explore some examples of using the LAST_VALUE function with numeric functions.

Example 1: Calculating a Running Total

Suppose you have a table called sales with columns date, product, and quantity. You want to calculate the running total of the quantity for each product over time.

SELECT
  date,
  product,
  quantity,
  LAST_VALUE(SUM(quantity)) OVER (PARTITION BY product ORDER BY date) AS running_total
FROM
  sales;

In this example, the LAST_VALUE function is used with the SUM function to calculate the running total of the quantity column for each product within the defined window ordered by date.

Example 2: Finding the Maximum Value

Let’s say you have a table called sensor_data with columns timestamp and temperature. You want to find the maximum temperature in a sliding window of the last 10 records.

SELECT
  timestamp,
  temperature,
  LAST_VALUE(temperature) OVER (ORDER BY timestamp ROWS BETWEEN 9 PRECEDING AND CURRENT ROW) AS max_temperature
FROM
  sensor_data;

In this example, the LAST_VALUE function is used to extract the value of the temperature column within the sliding window of the last 10 records, ordered by timestamp. This will give you the maximum temperature within the window.

Conclusion

The LAST_VALUE function in SQL can be a powerful tool when combined with numeric functions. It allows you to extract the last value in a windowed set of rows, enabling calculations such as running totals, finding maximum or minimum values, or tracking changes over time. Understanding how to utilize this function can greatly enhance your data analysis capabilities. #SQL #NumericFunctions