When working with SQL, you may often come across scenarios where you need to retrieve the first or last value in a column based on a specific order. In such situations, SQL provides two handy functions - LAST_VALUE and FIRST_VALUE. In this blog post, we will explore the differences between these two functions and understand when to use each one.

SQL LAST_VALUE

The LAST_VALUE function in SQL is used to retrieve the last value in a column based on the specified order. It is commonly used for calculating running totals, finding the latest record, and more.

Here’s a simple example that demonstrates the usage of LAST_VALUE:

SELECT id, name, salary, LAST_VALUE(salary) OVER (ORDER BY id)
FROM employees;

In this example, the LAST_VALUE function is applied to the “salary” column. The function is evaluated over the “id” column, ordering the rows in ascending order. It will return the last salary value in each row.

SQL FIRST_VALUE

On the other hand, the FIRST_VALUE function is used to retrieve the first value in a column based on a specified order. It is useful when you want to get the initial value or the earliest record in a set.

Here’s an example that demonstrates the usage of FIRST_VALUE:

SELECT id, name, salary, FIRST_VALUE(salary) OVER (ORDER BY id)
FROM employees;

In this example, the FIRST_VALUE function is applied to the “salary” column, similar to the previous example. However, by changing the order to ascending, it will return the first salary value in each row.

Conclusion

To summarize, SQL LAST_VALUE and FIRST_VALUE are powerful functions that allow you to retrieve the last and first values in a column based on a specified order. Whether you need to find the latest record or calculate running totals, these functions provide a simple and efficient solution.

Remember, LAST_VALUE is used to retrieve the last value, while FIRST_VALUE is used to retrieve the first value. Understanding the differences between these two functions will help you choose the right one for your SQL queries.

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