当您需要在 SQL Server 中利用 T-SQL 比较结果集的每一列跟前一列或后一列的差异时,在过去可能需要利用 CURSOR 搭配临时表变量,或是透过递归 CTE 来达到这个效果,如今 SQL Server 2012 提供了两个分析用的函数(LEAD、LAG)来让您更容易进行 ROW LEVEL 数据比较。 以下程序代码用来示范如何透过 LEAD 函数来计算...
提升開發人員效率的 T- SQL 新功能 - 分析函數 (Lead 和 Lag) Learn 登入 下載PDF Learn 閱讀英文 TwitterLinkedInFacebook電子郵件 發行項 2021/10/20 意見反應 > [!VIDEO https://www.microsoft.com/zh-tw/videoplayer/embed/de9151bb-d08a-4139-803a-25a28ea3d638]...
SQL Server Denali CTP3 finally gives us LAG and LEAD. Here is the description directly stolen from BOL:Accesses data from a previous row in the same result set without the use of a self-join in Microsoft SQL ServerCode-Named “Denali”, Community Technology Preview 3 (CTP 3)....
SELECTp.FirstName,p.LastName,ROW_NUMBER()OVER(ORDERBYa.PostalCode)AS'Row Number',RANK()OVER(ORDERBYa.PostalCode)AS'Rank',DENSE_RANK()OVER(ORDERBYa.PostalCode)AS'Dense Rank',NTILE(4)OVER(ORDERBYa.PostalCode)AS'Quartile',s.SalesYTD,a.PostalCodeFROMSales.SalesPerson sINNERJOINPerson.Person pONs...
其实LAG和LEAD还有两个可选参数,比如LAG(val, 3, 0)的意思就是,取向后的第三行,如果没有这样一行,就返回0。默认是LAG(column,1,NULL)。 然后是FIRST_VALUE和LAST_VALUE的例子: SELECTcustid, orderid, val,FIRST_VALUE(val)OVER(PARTITIONBYcustidORDERBYorderdate, orderidROWSBETWEENUNBOUNDED PRECEDINGAND...
中篇的重点在于,在复杂情况下使用表表达式的查询,尤其是公用表表达式(CTE),也就是非常方便的WITH AS XXX的应用,在SQL代码,这种方式至少可以提高一倍的工作效率。此外开窗函数ROW_NUMBER的使用也使得数据库分页变得异常的容易,其他的一些特性使用相对较少,在需要时再查阅即可。
SQL Server 2012 SolutionSQL Server 2012 and up offers a simpler alternative to the OUTER APPLY solution. In SQL Server 2012 the LEAD() and LAG() functions were introduced that allow us to avoid correlated subquery and transform that solution into this code:...
LAG & LEAD functions... Any Way to Retrieve the 1st non-NULL Values? Lag and Lead not recognized Large Dynamic SQL Statement being truncated. Large Table - Move to different Filegroup - Best and Fast way Last Login Date/Time of All SQL Server Logins From sys.server_principals Last Modifie...
LAG (Transact-SQL) LAST_VALUE (Transact-SQL) LEAD (Transact-SQL) PERCENT_RANK (Transact-SQL) PERCENTILE_CONT (Transact-SQL) PERCENTILE_DISC (Transact-SQL) 分析函数基于一组行计算聚合值。 但是,与聚合函数不同,分析函数可能针对每个组返回多行。 可以使用分析函数来计算移动平均线、运行总计、百分比或一...
Finally, I’ll demonstrate how new analytic functions in SQL Server 2012,LAGandLEAD, make it possible to find a solution that performs just as well, and requires a little less lateral thinking. Understanding the Business Requirements and Data ...