In SQL, the LAST_VALUE function can be used to retrieve the last value of a specified column within a group. This function is commonly used with the UPDATE statement to update a table with the last value of a column.

To demonstrate this, let’s consider a table called employees with the following structure:

CREATE TABLE employees (
  id INT,
  name VARCHAR(50),
  salary INT
);

Now, suppose we want to update the salary column of all employees in the table with their last recorded salary. We can use the LAST_VALUE function along with the UPDATE statement to achieve this.

The LAST_VALUE function requires the use of the OVER clause to define the ordering of the rows within a group. In this case, we can order the rows by the id column to ensure that the last value is selected.

Here’s an example SQL query that demonstrates how to update the salary column with the last recorded salary for each employee:

UPDATE employees
SET salary = LAST_VALUE(salary) OVER (ORDER BY id
                                      ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING);

In the above example, we specify the id column in the ORDER BY clause to ensure that the rows are ordered by the id column. The ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING clause ensures that the LAST_VALUE is calculated over all rows in the table.

By executing this SQL query, each employee’s salary column in the employees table will be updated with their last recorded salary.

In conclusion, the LAST_VALUE function in SQL can be used with the UPDATE statement to update a table column with the last value of a specified column. This is achieved by utilizing the OVER clause to define the ordering of rows within a group.