Window function (SQL)
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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:
<OVER_CLAUSE> :: =
OVER ( [ PARTITION BY <expr>, ... ]
[ ORDER BY <expression> ] )
The OVER clause can partition and order the result set. Ordering is used for order-relative functions such as row_number.
See also
External links
- Stefan DeBloch, Windowed Tables and Window function in SQL
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