COMPUTER SCIENCE AND ENGINEERING
SQL
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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True
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False
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Either A or B
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None of the above
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Detailed explanation-1: -They reduce the result set based on the aggregation. Window partitions can be defined to form groups of rows. They compute a value for each and every row in the window. They require the ‘over’ clause.
Detailed explanation-2: -What are Window Functions? Window functions enable users to perform calculations against partitions (i.e. subgroups or sections) of a result set, typically a table or the results from another query.
Detailed explanation-3: -A window function performs an aggregate-like operation on a set of query rows. However, whereas an aggregate operation groups query rows into a single result row, a window function produces a result for each query row: The row for which function evaluation occurs is called the current row.
Detailed explanation-4: -This order of operations implies that you can only use window functions in SELECT and ORDER BY . That is, window functions are not accessible in WHERE, GROUP BY, or HAVING clauses. For this reason, you cannot use any of these functions in WHERE : ROW NUMBER(), RANK(), DENSE RANK(), LEAD(), LAG(), or NTILE() .