MYSQL Basics__ Query language DQL

The first chapter is the basic syntax specification of SQL 1.sql is not case sensitive, but it is customary for keywords, system reserved words, function names to be uppercase, and table and column names to be lowercase 2.sql uses space or carriage return to separate each word. It is customary for ...

Posted on Mon, 29 Jun 2020 03:51:57 -0400 by weevil

MySQL 8.0 window function practice and summary

Before MySQL 8.0, it was quite painful to do data ranking statistics, because there was no window function like Oracle, SQL SERVER, PostgreSQL and other databases. However, with the addition of window functions in MySQL 8.0, it is no longer a problem for this kind of statistics. This paper introduces MySQL window functions with common sorting e ...

Posted on Sat, 27 Jun 2020 03:42:25 -0400 by always_confused

Technology sharing, semi consistent reading and optimization of Update

Author: Zhao Liming Aikesheng, a member of MySQL DBA team, Oracle 10g OCM, MySQL 5.7 OCP, is good at database performance problem diagnosis, transaction and lock problem analysis, and is responsible for dealing with the problems in the daily operation and maintenance of customer MySQL and our company's self-developed DMP platform, and is very ...

Posted on Tue, 23 Jun 2020 06:07:02 -0400 by ultraviolet_998

java null pointer exception: the root of the problem and the solution

@Java null pointer exception Exception in thread "main" java.lang.NullPointerException In the previous writing experiment, we encountered a java null pointer exception problem. After multiple queries of data, China and Vietnam solved the exception, so we decided to record the solution of this exception. ...

Posted on Sun, 14 Jun 2020 05:25:00 -0400 by Crys

Analysis of HOT principle

2020-06-09 19:31:01 1, Questions Some time ago, someone in the QQ group was confused about "I update d the data in this row of table (0,4), looked at the page data of the index, and found that the index always points to (0,4), and I can't find the data by querying the business table with ctid='(0,4)"; then I made the vacuum of the ...

Posted on Tue, 09 Jun 2020 23:11:28 -0400 by niki

Simple configuration of mysql database master-slave synchronization, read-write separation

This paper is learning notes, mainly used to record my learning process. Part of the content for reprint!!!! 1, What are the reasons for Mysql's Master-Slave synchronous replication, read-write separation? For some current large-scale websites, only one database server is not enough to handle a lar ...

Posted on Sun, 07 Jun 2020 23:59:55 -0400 by koughman

Host transfers files to KVM virtual machine via FTP

Machine environment: Host: ubuntu16.04 KVM version: QEMU emulator version 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.16) Virtual Machine: Ubuntu-Server 16.04.3 LTS Install FTP, File Transfer in ubuntu Server The network is connected.Install openssh server $sudo apt-get install openssh-server $sudo apt-get install openssh-sftp-server Install ...

Posted on Sun, 07 Jun 2020 12:48:28 -0400 by Profector

ORM Framework Series of Wheelmaking Motion~Talk about ORM Framework in my mind

ORM Conceptual Analysis First, comb out the concept of ORM. The spelling of ORM is Object Relation Mapping (Object Relation Mapping), where Object is the object in Object-Oriented Language. This paper uses c# language, so it is a.net object. Relation Mapping is a relationship mapping, which refers to the relationship mapping between.net object ...

Posted on Wed, 03 Jun 2020 22:04:41 -0400 by Major Tom

What is PL/SQL? How to use it?

PL/SQL 1. What is PL/SQL? PL/SQL (Procedure Language/SQL) is a procedural extension of Oracle to SQL language. It refers to the addition of process processing statements (such as branch / condition, loop, variable, type, etc.) in SQL command language, which makes SQL language have process processing ability. By combining the data manipulatio ...

Posted on Wed, 03 Jun 2020 13:02:44 -0400 by wkoneal

ORACLE EMCC 12.1.0.5 installation configuration

1. Linux 6 + emcc12.1.0.5 installation environment introduction l this set of environment is based on rhel6.10 + Oracle 11.2.0.4 single node database L java development kit (JDK)1.6.0.43.0 L Oracle WebLogic Server 11g version 1 (10.3.6) Orac l e Management Office 12c 5th Edition (12.1.0.5) 1.1 check users, groups $ more /etc/oraInst.loc inve ...

Posted on Tue, 02 Jun 2020 12:54:47 -0400 by HavokDelta6