In MySQL, we can convert NOT EXISTS statement to LEFT JOIN statement to optimize. Why is there performance improvement?
Using NOT EXISTS mode, SQL is as follows:
FROM t_monitor m
WHERE NOT exists
FROM t_alarm_realtime AS a
AND a.monitor_na ...
Posted on Tue, 25 Dec 2018 00:36:07 -0800 by dxdolar
MySQL Group Replication (MGR) is a new high availability and high scalability solution launched by MySQL in December 2016. MySQL group replication provides high availability, high scalability and high reliability MySQL cluster services.
1. Introduction to MGR
Write More, Write Conflict Detection
Excellent scalability, dyna ...
Posted on Mon, 24 Dec 2018 17:06:06 -0800 by Froolah
#MySQL Access denied for user 'root'@'localhost'
Causes of the problem:
Execution of orders
CREATE USER goodboy IDENTIFIED BY 'goodboy';
GRANT ALL privileges ON *.* TO 'goodboy'@'%' identified by 'goodboy' WITH GRANT OPTION;
Errors occurred when granting all database privileges to goodboy users
ERROR 1045 (28000): ...
Posted on Mon, 24 Dec 2018 14:09:07 -0800 by schwa97
Percona Toolkit contains a variety of tools for MySQL database management.
Following is a description of the common use of pt-online-schema-change and pt-archiver with RDS MySQL.
Both pt-online-schema-change and pt-archiver tools must specify the no-version-check option to be used with RDS MySQL instances.
This sample is tested using ve ...
Posted on Sun, 23 Dec 2018 23:33:06 -0800 by ThaboTheWuff
In previous articles, I have explained threadmodel, socket tcp, socket http, log, astart, scripts;
All of them are explanations in fragments. From today on, we will take you a glimpse of the net.sz.framework framework.
net.sz.framework framework is divided into java version and C net version, and the two language versions keep high cons ...
Posted on Sun, 23 Dec 2018 13:48:06 -0800 by snafudawn
Meow a Mimi's blog: w-blog.cn
EMQ official address: http://emqtt.com/
EMQ Chinese Documents: http://emqtt.com/docs/v2/guide.html
1.TLS Certificate Verification
In order to ensure security, we often use HTTPS to ensure that requests are not tampered with, and TLS encryption as MQTT to ensure transmission security.
The default TLS encr ...
Posted on Sun, 23 Dec 2018 02:24:06 -0800 by pythian
The abnormal information is as follows:
--- The error occurred in mit/datamodel/ibatis/person.xml.
--- The error occurred while executing query.
--- Check the select * from person where pID = ?.
--- Check the SQL Statement (preparation failed).
--- Cause: com.mysql.jdbc.exception ...
Posted on Sat, 22 Dec 2018 11:06:06 -0800 by daanoz
A Demo runs very hard and the environment is not clear. It always encounters problems of one kind or another, such as the following:
1. value '1.8' is not a valid language level error
2. Unsupported major.minor version 51.0
Therefore, this article begins by explaining environmental dependence:
Drools 6.5.0 http://www.drools.o ...
Posted on Fri, 21 Dec 2018 06:12:05 -0800 by joeywoodbury
Nginx characteristicsNginx has the advantages of stable performance, rich functions, simple operation and maintenance, fast processing of static files and little system resource consumption.1. Compared with Apache, Nginx serves as a Web server: it uses fewer resources, supports more concurrent connections and is more efficient.2. As a load bala ...
Posted on Thu, 20 Dec 2018 22:03:06 -0800 by russian_god
Understanding Abstract factories
In ADO.NET, the operation steps of SqlServer, Mysql and so on are similar, but the difference is:
SqlServer uses SqlConnection, SqlCommand, SqlData Adapter for its operation.
MySql uses MySql Connection, MySqlCommand, MySqlDataAdapter, and these connection classes of operation classes ...
Posted on Thu, 20 Dec 2018 17:12:05 -0800 by j05hr