T-SQL window functions allow you to perform data analysis calculations like aggregates, ranking, offset and more. When compared with alternative tools like grouping, joins and subqueries, window functions have several advantages that enable solving tasks more elegantly and efficiently. Furthermore, window functions can be used to solve a wide variety of T-SQL querying tasks well beyond their original intended use case, which is data analysis. This session introduces window functions and their evolution from SQL Server 2005 to SQL Server 2017, explains how they get optimized, and shows practical use cases.
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Presented by Itzik Ben-Gan at SQLBits XVII