SQL Server Performance Blog where milliseconds matter

Hi guys, In the last four posts we talked about the T-SQL news that SQL Server 2022 brought us. SQL Server 2022 and the DATE_BUCKET function. Work more easily with dates  SQL Server 2022 and the GREATEST / LEAST T-SQL commands   SQL Server 2022 and the STRING_SPLIT command .. string splitting made easy!  SQL Server 2022 and the GENERATE-SERIES command .. a T-SQL language enhancement  Today we will talk about another T-SQL extension.  We will talk about the Window clause in the window functions . As always, I will try to be as clear as possible! Enjoy this post!   The Window Clause With SQL Server 2022, Microsoft introduce in the window functions the concept of window . For the sake of truth this is not a feature invented by Microsoft because this concept is part of the ISO/IEC SQL standard. If you doesn't know what a window function is, you can read here: Learn SQL Server Window functions and Running Totals in five minutes  Looking at the example bel...

Hi Guys, In the last post we talked about the Lazy Spool operator , today to continue the discussion we will talk about another type of spool: the window spool . We will tell how it works and when the optimizer uses this type of spool. Enjoy the reading!   The window spool Let's say the window spool is both a logical and a physical operator. The optimizer uses this type of spool when dealing with a query that contains a Windows function . I am sure you already know what a windows function is, ...but in case there is someone just entered in the SQL world I gladly remember it .. A window function is simply a function that can operate on a set of rows and return a single aggregated value for each row. For example i can compute an aggregate value without group data. The highlighted part of the string is the window function: SELECT [NAME], [SALARY], MAX ([SALARY]) OVER ( PARTITION BY [NAME] ORDER BY [NAME]) AS MAX_SALARY FROM [EMPLOYEE] order by [NAME], [SALARY] This function return...