In SQL, the LAST_VALUE function is used to get the last value in a group or window. When combined with the LEAD function, it allows you to retrieve the next value in a sequence, making it a powerful tool for analyzing data in a specific order.

Syntax of LAST_VALUE with LEAD

The syntax for using LAST_VALUE with LEAD is as follows:

LAST_VALUE(expression) OVER (PARTITION BY partition_expression ORDER BY order_expression ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

Here:

• expression is the column or expression to get the last value of
• PARTITION BY defines the grouping of the data
• ORDER BY specifies the order of the data within each group
• ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ensures that the window includes all rows from the start of the partition up to and including the current row

Example usage

Suppose we have a table called employees with the following data:

We can use LAST_VALUE with LEAD to find the next highest salary for each employee in order:

SELECT name, salary, LAST_VALUE(salary) OVER (ORDER BY salary) AS next_highest_salary
FROM employees

The result would be:

In the above example, the LAST_VALUE function is applied on the salary column, and the LEAD function orders the result set by the salary. It retrieves the next highest salary for each employee.

Conclusion

Using the LAST_VALUE function with the LEAD function allows you to access the last value in a group or window while also retrieving the next value in a sequence. This can be useful in various scenarios, such as identifying trends or comparing values.