In SQL, the LAST_VALUE function allows us to access the last value in a set of ordered rows within a partition. By default, this function returns the last non-null value. However, there may be scenarios where we want to consider NULL values as the most recent, and order them at the beginning of the result set. In such cases, we can leverage the NULLS FIRST option with the LAST_VALUE function.

Here’s an example query that demonstrates the usage of LAST_VALUE with NULLS FIRST:

SELECT column1, column2,
    LAST_VALUE(column3) 
         OVER (PARTITION BY column1 ORDER BY column2 
         ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
         NULLS FIRST) AS last_value_with_nulls_first
FROM your_table;

In the above query, we retrieve values from column1, column2, and apply the LAST_VALUE function on column3. Sorting is done within each partition defined by column1, ordering the rows by column2 in ascending or descending order. By adding NULLS FIRST at the end of the ORDER BY clause, NULL values will be considered the “last” values within the partition.

It’s important to note that the NULLS FIRST option is not supported in all database systems. So, be sure to consult your SQL database documentation to ensure compatibility.

With the LAST_VALUE function and the NULLS FIRST option, you can conveniently handle scenarios where treating NULL values as the most recent is crucial for your analysis or application.

#SQL #LAST_VALUE #NULLS_FIRST