<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…

descriptive statistics:组织和总结信息,为自身(可以是population也可以是sample)审视和探索, inferential statistics.从sample中推论population情况并评价推论可信度 在population中精挑细选出sample Observational Studies:观察  and Designed Experiments:施加控制和影响,再观察 Observational studies can reveal only assoc…

1.Normal distribution In probability theory, the normal (or Gaussian or Gauss or Laplace–Gauss) distribution is a very common continuous probability distribution. Normal distributions are important in statistics and are often used in the natural and…

Statistics in Hive Statistics in Hive Motivation Scope Table and Partition Statistics Column Statistics Top K Statistics Implementation Usage Configuration Variables Newly Created Tables Existing Tables Examples Current Status (JIRA) This document de…

一朋友使用autotrace查看数据库执行计划发现结果如下,Statistics中很多信息为0,这个肯定是不正常现象,什么都可以为0,consistent gets也不可能为0. SQL> set autot on SQL> select count(*) from RACV_DATA.PARTY_DUMMY;     COUNT(*) ----------         47   Elapsed: 00:00:00.00   Execution Plan -----------------…

Statistics in Python Materials for the “Statistics in Python” euroscipy 2015 tutorial. Requirements Standard scientific Python environment (numpy, scipy, matplotlib) Pandas Statsmodels Seaborn To install Python and these dependencies, we recommend th…

最近阅读SQLskills SQL101,将Erin Stellato部分稍作整理.仅提取自己感兴趣的知识点,详细内容请阅读原文. 一.Trace Flags推荐开启三个跟踪标记1118.3023.3226跟踪标记1118(适用2016之前版本),避开对SGAM页的使用,在统一区分配新建对象的空间.跟踪标记3023(适用2014之前版本),在默认情况下对实例上进行的所有备份启用CHECKSUM选项.跟踪标记3226,成功备份信息不再写入SQL Server ERRORLOG 启动参数添加:-T3…

一.常用的视图 1.会话相关视图 View Description V$PROCESS Contains information about the currently active processes V$SESSION Lists session information for each current session V$SESS_IO Contains I/O statistics for each user session V$SESSION_LONGOPS Displays the…

The Basics of Probability Probability measures the amount of uncertainty of an event: a fact whose occurence is uncertain. Sample space refers to the set of all possible events, denoted as . Some properties: Sum rule: Union bound: Conditional probabi…

统计学中最常见的几种概率分布分别是正态分布(normal distribution),t分布(t distribution),F分布(F distribution)和卡方分布(χ2 distribution,chi-square distribution),其中后三种属于抽样分布. 为什么要研究概率分布呢?因为通过研究概率分布,我们可以找出数据的分布规律,并根据这些规律来解决特定条件下的问题.比如:假设随机变量X服从某个已知的分布,我们就可以利用这个分布对X的取值是否显著异于分布期望值进行检验.…