Window Function
A window function in SQL:2003 is an aggregate function applied to a partition of the result set.
For example,
sum(population) OVER( PARTITION BY city )calculates the sum of the populations of all rows having the same city value as the current row.
Partitions are specified using the OVER clause which modifies the aggregate. Syntax:
The OVER clause can partition and order the result set. Ordering is used for order-relative functions such as row_number.
Read more about this topic: Select (SQL)
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