type column parsing of explain

1,const Indicates that the execution step returns at most one row of data. const usually appears in the equivalent query of the primary key or unique index, such as the equivalent query of the primary key id of the t table:It can be considered that it is as fast as a rocket to locate a record by comparing the equivalence between the primary key ...

Posted on Sun, 31 May 2020 11:54:35 -0400 by peter_anderson

Alibaba cloud Centos7 deploys Java web [jar/war/virmach+vps + domain name service]

(1) Part 1: basic jar package running (Tomcat does not need to be configured) [http://60.205.183.114:8081/] 1. Configure Alibaba cloud (Esc student server, image Centos7.7) and connect to the terminal remotely. 2. Install and configure the JDK (refer to https://www.jianshu.com/p/093413f2a04f)a) Install the jdk. b) Find the jdk path configurat ...

Posted on Sun, 31 May 2020 11:37:58 -0400 by LuAn

mysql count(*) count count(id) explanation

Environment wins10 8g memory mysql5.7.27 mysql my.ini Configuration note (innodb_flush_log_at_trx_commit=0) configuration [Client] #Set 3306 port port = 3306 [mysqld] #Set 3306 port port = 3306 # Set the installation directory of mysql basedir=E:devmysql-5.7.27-winx64 # Set the storage directory of mysql database data datadir=E:devmysql-5.7.2 ...

Posted on Sun, 31 May 2020 10:10:15 -0400 by cofey12681

Summary of JDBC basic knowledge

Refer to the summary of Java language programming foundation version 10 Main interface 1 Basic JDBC program 2. The main methods of initializeDB and showGrade are to access the database from JavaFX Statement 1PreparedStatement interface inherits from Statement interface to create parameterized SQL Statement Exa ...

Posted on Sun, 31 May 2020 04:35:47 -0400 by cpharry

The modified character set code of MySQL 5.6 under Linux is UTF8 (to solve the problem of Chinese code scrambling, it can be used for personal test!)

The modified character set code of MySQL 5.6 under Linux is UTF8 (to solve the problem of Chinese scrambling) 1, Log in to MySQL to view SHOW VARIABLES LIKE 'character%'; the following character set is displayed as follows:+--------------------------+----------------------------+ | Variable_name | Value | +--------------------------+---------- ...

Posted on Sun, 31 May 2020 01:13:44 -0400 by driverdave

How to store IP address effectively in MySQL

A few days ago, a friend of a Miao went for an interview. He came back and told me that the interviewer asked him how his IP address existed in the database? At that time, he didn't think much about it. He replied directly to save string After all, the IP address is a string, and it's OK to store it in the database as a character type. But, a ...

Posted on Sat, 30 May 2020 03:46:53 -0400 by gavinr98

Use port forward to access the applications in the cluster, taking Redis as an example

Create Deployment and Service for Redis Create Redis Deployment. YAML file is as follows: apiVersion: apps/v1 kind: Deployment metadata: name: redis-master labels: app: redis spec: selector: matchLabels: app: redis role: master tier: backend replicas: 1 template: metadata: labels: app: re ...

Posted on Sat, 30 May 2020 02:08:17 -0400 by gsv2com

A single example of PHP PDO and mysql connection to prevent timeout

This database class mainly deals with creating database objects in single instance mode. If there are two long-time intervals to execute sql operations, the problem of connection failure will occur when processing again. A cache array is used to store pdo objects and timestamps, and the time between the two executions is compared. If the interv ...

Posted on Fri, 29 May 2020 04:02:35 -0400 by kaveman50

ES7 learning notes GEO location search

The basic content of ES is almost introduced. At last, let's take a look at GEO location search. Now most apps have location-based search functions. For example, when we order takeout, we can sort it according to the distance from us, which can save our delivery fee and delivery time. When we look for work, we can also sort it according to the ...

Posted on Fri, 29 May 2020 03:43:29 -0400 by micklerlop

Introduction to Canal - server configuration

Canal is a framework (component) provided by Alibaba for incremental log analysis of MySQL database, providing incremental data subscription and consumption. 1. Configure MySQL configuration file( my.ini ), add the following configuration: [mysqld] log-bin=mysql-bin #Enable log monitoring binlog-format=ROW #Monitoring mode is ROW server_id=1 ...

Posted on Thu, 28 May 2020 11:25:20 -0400 by jstngk