In SQL, the LAST_VALUE function is used to return the last value in a set of rows. This can be useful when you want to find the most recent record or the latest update in a table.

The EXCEPT statement is used to combine the result sets of two queries and return only the distinct rows that are present in the first query but not in the second query.

Syntax

LAST_VALUE (expression) OVER (PARTITION BY column ORDER BY column [ASC|DESC] ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)

Example

Consider a table called employees with the following structure:

If you want to find the last recorded salary for each employee, you can use the LAST_VALUE function along with the EXCEPT statement. Here’s an example query:

SELECT employee_id, name, salary
FROM (
    SELECT employee_id, name, salary,
        LAST_VALUE(salary) OVER (
            PARTITION BY employee_id
            ORDER BY employee_id ASC
            ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
        ) as last_salary
    FROM employees
) AS subquery
WHERE salary != last_salary

In the above query, we use the LAST_VALUE function to get the last salary value for each employee. Then, we use the EXCEPT statement to exclude the rows where the salary is equal to the last recorded salary.

This query will return the rows where the salary has changed for each employee:

In conclusion, by combining the LAST_VALUE function with the EXCEPT statement, you can easily find the rows where a specific column value has changed in a table. This can be particularly useful when working with historical or time-based data.

#SQL #LASTVALUE #EXCEPT