SQL LAST_VALUE with conditional functions

28 Sep 2023

In SQL, the LAST_VALUE function is used to retrieve the last value in an ordered set of data. It can also be combined with conditional functions to apply certain conditions when retrieving the last value. In this blog post, we will explore how to use the LAST_VALUE function with conditional functions in SQL.

Syntax of LAST_VALUE Function

The LAST_VALUE function is commonly used with the OVER clause in SQL. Here is the general syntax of the LAST_VALUE function:

LAST_VALUE(expression) OVER (PARTITION BY column_name ORDER BY column_name [ASC|DESC])

The expression parameter represents the column or expression from which we want to retrieve the last value. The PARTITION BY clause allows us to divide the data into groups, while the ORDER BY clause specifies the order in which the data is evaluated.

Using LAST_VALUE with SQL Conditional Functions

To apply conditional functions to the LAST_VALUE, we use a combination of CASE and WHERE clauses. Let’s see a few examples:

Example 1: Retrieve the last salary of male employees

SELECT
  employee_id,
  LAST_VALUE(salary) OVER (PARTITION BY gender ORDER BY hire_date DESC) AS last_salary
FROM
  employees
WHERE
  gender = 'M'

In the above example, we use LAST_VALUE to retrieve the last salary of male employees. The PARTITION BY gender clause divides the data into groups based on gender, and the ORDER BY hire_date DESC clause orders the data by hire date in descending order. The WHERE clause filters the data to retrieve only male employees.

Example 2: Retrieve the last product quantity sold for each category

SELECT
  category,
  product,
  quantity,
  LAST_VALUE(quantity) OVER (PARTITION BY category ORDER BY order_date DESC) AS last_sold_quantity
FROM
  sales

In this example, we use LAST_VALUE to obtain the last product quantity sold for each category in the sales table. The PARTITION BY category clause groups the data by category, while the ORDER BY order_date DESC clause sorts the data by order date in descending order.

Conclusion

The LAST_VALUE function in SQL allows us to retrieve the last value in an ordered set of data. When combined with conditional functions like CASE and WHERE, we can apply conditions to retrieve specific values based on different criteria. By using this powerful combination, we can efficiently perform data analysis and make informed decisions in SQL queries.

#SQL #LAST_VALUE #ConditionalFunctions