In SQL, the LAST_VALUE function can be used to retrieve the last value in a partition. This function is particularly useful when working with scalar types, where you want to get the last value based on a specific order.

Syntax

The syntax for using LAST_VALUE with scalar types is as follows:

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

The expression specifies the value that you want to retrieve the last value of. The column is the partitioning column that helps group the data, and the order_column is the column used to determine the order in which the last value is calculated.

Example

Let’s consider a hypothetical scenario where we have a table called orders with the following structure:

+----+------------+-------+
| ID |    Date    | Value |
+----+------------+-------+
| 1  | 2021-01-01 |  100  |
| 2  | 2021-01-02 |  200  |
| 3  | 2021-01-03 |  300  |
| 4  | 2021-01-04 |  400  |
| 5  | 2021-01-05 |  500  |
+----+------------+-------+

Suppose we want to retrieve the last value for each distinct date. We can use the LAST_VALUE function in the following way:

SELECT DISTINCT
  Date,
  LAST_VALUE(Value) OVER (PARTITION BY Date ORDER BY ID ASC) AS LastValue
FROM
  orders;

This query will give us the following result:

+------------+-----------+
|    Date    | LastValue |
+------------+-----------+
| 2021-01-01 |    100    |
| 2021-01-02 |    200    |
| 2021-01-03 |    300    |
| 2021-01-04 |    400    |
| 2021-01-05 |    500    |
+------------+-----------+

The LAST_VALUE function helps to obtain the last value for each date by ordering the records based on the ID column in ascending order.

Conclusion

Using the SQL LAST_VALUE function with a scalar type allows you to retrieve the last value in a partition based on a specific order. This can be a powerful tool when working with datasets where the order of data is crucial. By understanding the syntax and incorporating it into your queries, you can easily obtain the desired results. #SQL #LAST_VALUE