In SQL, the LAST_VALUE function is used to retrieve the last value from a specified column within a partition, based on the order specified in the ORDER BY clause. The FETCH statement can be used to limit the number of rows returned by a query.

Syntax:

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

Here’s an example to demonstrate the usage of LAST_VALUE with the FETCH statement:

Scenario: Suppose we have a table named orders that stores records of orders placed by customers. We want to retrieve the last order amount for each customer.

SQL Query:

SELECT customer_id, order_amount
FROM
    (SELECT customer_id, order_amount,
            ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn
     FROM orders) AS subquery
WHERE rn = 1
FETCH FIRST ROW ONLY;

Explanation:

• We use the inner query to assign a row number to each order for every customer, based on the order date in descending order.
• The outer query selects the customer_id and order_amount from the inner query, filtering only the rows with row number 1 (which corresponds to the last order for each customer).
• The FETCH FIRST ROW ONLY clause limits the result to only the first row.

By using the LAST_VALUE function in combination with the FETCH statement, we can efficiently retrieve the last value from a specific column within a partition. This can be very useful when working with large datasets or when analyzing time-series data.

#SQLtips #FetchStatement