In SQL, the LAST_VALUE function is used to return the last value within a group or window frame. It can be combined with the LAG function to retrieve the previous row’s value.

The LAG function is used to get the value of a column from the previous row in the result set. By combining these two functions, we can access the last value of the previous row.

Here’s an example of how to use LAST_VALUE with LAG function in SQL:

SELECT column_name, 
       LAG(column_name) OVER (ORDER BY order_column) AS previous_value,
       LAST_VALUE(column_name) OVER (PARTITION BY partition_column ORDER BY order_column) AS last_value
FROM table_name;

In the above example:

• column_name is the name of the column we want to retrieve values from.
• order_column is the column used to determine the order. It is used in both the LAG and LAST_VALUE functions.
• partition_column is an optional column used for partitioning the result set. It is only required if you want to retrieve the last value within each partition.

By using LAG(column_name) OVER (ORDER BY order_column), we can retrieve the previous row’s value in the result set. And by using LAST_VALUE(column_name) OVER (PARTITION BY partition_column ORDER BY order_column), we can retrieve the last value within each partition.

Note that the LAG function requires an ORDER BY clause to determine the order of rows. The LAST_VALUE function can use both ORDER BY and PARTITION BY clauses.

With the help of these functions, you can efficiently retrieve the previous row’s value and the last value within a partition.

#SQL #LAGFunction #LASTVALUE