Hello this is Gulshan Negi

Well, in short, the OVER() function in SQL is used in conjunction with aggregate functions such as SUM(), AVG(), COUNT(), and MAX(), to calculate the aggregate values for a specific set of rows within the result set.

Thanks  

In SQL, the OVER() clause is used with aggregate functions to perform calculations on a subset of rows within a result set, called a partition. The OVER() clause specifies the partitioning and ordering of the rows before the calculation is performed.

The OVER() clause has two components: the PARTITION BY clause and the ORDER BY clause. The PARTITION BY clause divides the result set into partitions based on one or more columns, and the ORDER BY clause determines the order of rows within each partition.

The OVER() clause with the PARTITION BY clause is particularly useful for calculating running totals, rankings, and other cumulative aggregates. For example, suppose you have a table of sales data with columns Year, Month, Product, and SalesAmount. You can use the OVER() clause to calculate the running total of sales amount for each product over each year, as follows:

SELECT    Year,    Product,    Month,    SalesAmount,    
SUM(SalesAmount) OVER(PARTITION BY Year, Product ORDER BY Month) AS RunningTotal 
FROM    SalesData 
ORDER BY    Year,    Product,    Month;

In this example, the OVER() clause partitions the sales data by Year and Product and orders the rows within each partition by Month. The SUM() function is then applied to the SalesAmount column over each partition, returning the running total of sales amount for each product over each year.

The output of this query will contain columns Year, Product, Month, SalesAmount, and RunningTotal. The RunningTotal column will contain the cumulative sum of SalesAmount for each Year and Product up to the current Month.

Overall, the OVER() clause allows more complex calculations and analysis of data within a result set.