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SQL Server - Lead and Lag Function

Overview In this part of the tutorial, we’ll look at offset functions, especially the LAG and LEAD functions. They were introduced in SQL Server 2012 and they made writing specific patterns in T-SQL much easier. With those functions, complex queries using self-joins or cursors can be replaced with easier queries. LAG and LEAD The LAG function has the ability to fetch data from a previous row, while LEAD fetches data from a subsequent row. Both functions are very similar to each other and you can just replace one by the other by changing the sort order. The LAG/LEAD function has also two optional parameters: The offset. The default is 1, but you can jump back more rows by specifying a bigger offset. You cannot specify a negative value. A default value. When there is no previous row (in the case of LAG), NULL is returned. You can see this in the screenshot in the first row. You can specify a default value to be returned instead of NULL. #practicalit #sqlleadandlagfunction #sql