1.前言 对于优化SQL语句或存储过程,以前主要是用如下语句来判断具体执行时间,但是SQL环境是复杂多变的,下面语句并不能精准判断性能是否提高:如果需要精确知道CPU.IO等信息,就无能为力了. ),) ),) 这时候如果使用SET STATISTICS TIME ON和SET STATISTICS IO ON 指令就能清楚的知道了,在测试之前需执行下面2条命令 DBCC DROPCLEANBUFFERS 清除缓冲区 DBCC FREEPROCCACHE 删除计划高速缓存中的元素 2.测试  2…

1.前言 对于优化SQL语句或存储过程,以前主要是用如下语句来判断具体执行时间,但是SQL环境是复杂多变的,下面语句并不能精准判断性能是否提高:如果需要精确知道CPU.IO等信息,就无能为力了. 1 2 3 PRINT convert(varchar(30),getdate(),121) select * from Sales.SalesOrderDetail where SalesOrderID > 64185 PRINT convert(varchar(30),getdate(),121)…

1.前言 对于优化SQL语句或存储过程,以前主要是用如下语句来判断具体执行时间,但是SQL环境是复杂多变的,下面语句并不能精准判断性能是否提高:如果需要精确知道CPU.IO等信息,就无能为力了. ),) ),) 这时候如果使用SET STATISTICS TIME ON和SET STATISTICS IO ON 指令就能清楚的知道了,在测试之前需执行下面2条命令 DBCC DROPCLEANBUFFERS 清除缓冲区 DBCC FREEPROCCACHE 删除计划高速缓存中的元素 2.测试  2…

原题链接在这里:https://leetcode.com/problems/statistics-from-a-large-sample/ 题目: We sampled integers between 0 and 255, and stored the results in an array count:  count[k] is the number of integers we sampled equal to k. Return the minimum, maximum, mean, m…

题目如下: We sampled integers between 0 and 255, and stored the results in an array count:  count[k] is the number of integers we sampled equal to k. Return the minimum, maximum, mean, median, and mode of the sample respectively, as an array of floating…

<Pro SQL Server Internals> 作者: Dmitri Korotkevitch 出版社: Apress出版年: 2016-12-29页数: 804定价: USD 59.99装帧: PaperbackISBN: 9781484219638 统计 SQL Server查询优化器在为查询选择执行计划时使用基于成本的模型.它估计不同执行计划的成本,并选择成本最低的一个.但是,请记住,SQL Server并不搜索查询可用的最佳执行计划,因为评估所有可能的替代方案在CPU方面都是耗时…

转载: http://www.cnblogs.com/xqhppt/p/4041799.html…

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