datacamp statistics

A push iOS Advanced research engineer Small BagObjectiveWith the rapid development of the mobile internet market, the former "Happy Rodeo" style of rough operation era has become the past. The change of the big environment also leads to the data statistic analysis of the mobile end plays more and more important role in the product research and development, the decision-making, the operation and so on, "the fine operation" has become the hot word for a time-from the factory to the entrepreneurial

statistics on non-indexed columnsSometimes, there may not be an index on a column in a join or filter condition. Even for such non-indexed columns, if the query optimizer knows the data distribution (statistics) of these columns, it is also likely to make the best choice.In addition to the statistics on the index, SQL Server can establish

Tags: drop ora way and data test var sub glob In the recent study of Oracle statistics, the method for collecting statistics is as follows:Dbms_stats. Gather_table_stats (Ownname VARCHAR2,---owner name tabname VARCHAR2,---table name partname VARCHAR2 DEFAULT NULL,---The partition name to parse Estimat E_percent number DEFAULT NULL,---the scale of the sample block_sample BOOLEAN default FALSE,---whether bloc

Tags: why sequential images use text also margin analysis The source of this article: http://www.cnblogs.com/wy123/p/6008477.html For statistics on the number of rows of data estimates, previously written on the non-related columns (separate or separate index columns) of the algorithm, refer to here.Today, let's write the statistical information on the calculation methods and potential problems of the composite index at the time of estimation.This pap

Introduction The SQL Server Query analyzer is overhead-based. Generally, the query analyzer determines how to select an efficient query route based on the predicate, such as the index to be selected. When the analyzer looks for a path, it does not count the number of rows and ranges of values contained in the index every time, instead, the information is created and updated based on certain conditions and saved to the database. This is the so-called statistical information. How to view

If we want the CBO to use the statistics of reasonable use of the data to correctly determine the quickest way to execute any SQL query, it is necessary to use the Analyze command or dbms_stats the statistics of the data in a timely manner.For example, in the index skip scan example, if you do not collect statistics for table employee and index, it is not the ind

However, statistics are inaccurate after dbms_stats analysis on some forums, and some bugs are found on dbms_stats (which may be related to the version, which is to be checked ). However, statistics are inaccurate after dbms_stats analysis on some forums, and some bugs are found on dbms_stats (which may be related to the version, which is to be checked ). Use dbms_stats or analyze Since Oracle8.1.5 int

Comparison | traffic | Statistics recently tried a few traffic statistics tools, a rough comparison, the improper place to look at: 163 Traffic Statistics: (not fully tested) 　　 Advantages: Almost no ads, page clean 　　 Disadvantages: 1, the location is not brilliant 　　 2, after installation, the Web page display speed has been reduced, browser alarm "block

Label: CREATE OR REPLACE PROCEDURE schameb.prc_gather_stats Current_User is BEGIN SYS. Dbms_stats. Gather_table_stats ('schname'TableName' CASCADE= TRUE); END ; / Select Owner,table_name,last_analyzed,num_rows from dba_tables where owner= ' SYSTEM ' and Table_name= ' aq$_internet_agents ' Last_analyzed: The last time the information of related tables is counted; Num_rows: Number of records in the table stored in the optimizer (may not match the actual situation ) When you EXEC the

Parameters related to MySQL statistics:1. Innodb_stats_on_metadata (whether statistics are automatically updated), the default is off in MySQL 5.7Takes effect only when the statistics are configured as non-persistent.That is, when the innodb_stats_persistent is configured to OFF, the Innodb_stats_on_metadata's settings are not valid until the hand that stores the

This article describes how to use distribution statistics in the DB2 optimizer? We all know that the DB2 optimizer is a cost-based optimizer. It makes a decision based on the statistical information of the table and the actual operation index. DB2 not only provides basic statistics, but also allows the creation of so-called distribution statistics. This article e

System statistics mainly describe some features related to system hardware, such as the performance and utilization of cpu and io systems. This information is very important for the query optimizer. During the execution plan selection process, the oracle optimizer uses the system statistics to evaluate the cost of the execution plan. Therefore, accurate system statistic