MySQL

One. Char and varcharChar is a fixed-length query that is faster than the varchar speed . The disadvantage of char is that it wastes storage space .When retrieving a char column, the returned result removes trailing spaces , so the program needs to

In the borrowing table and the reader table there is such a relationship, if you add a data in the borrowing table, the corresponding cumulative borrowing field in the reader table is increased by 1, if you delete a data in the borrowing table, the

Database introduction, Common classification Getting started with MySQL MySQL installation configuration MySQL multi-instance installation configuration MySQL Common basic commands MySQL database backup and recovery MySQL Log

MySQL Database supports the replication of one-way, two-way, chained cascade, ring-like, and different business scenarios. During the replication process, one server acts as the primary server, receives content updates from the user, and one or more

Database P3306CREATE DATABASE [if not EXISTS] db_name [characterset GBK];Use database;//Jump databaseshow databases;Alert Database db_name Character Set utf8;//modifieddrop databases [if not EXISTS] dbname;//Most usefulShow Create Databses

1. Create a database with tools Scrapy2. Create a Douban table in the Scrapy databaseint primary key auto_increment, name varchar (+) NOT NULL, author varchar () null, press Varc Har (+) NULL, date varchar (() NULL, page varchar () NULL, price

First:Check if Bin_log is turned onMysql> Show variables like ' Log_bin ';+---------------+-------+| variable_name | Value |+---------------+-------+| Log_bin | On |+---------------+-------+How does the Binlog function open?[[email protected] 3306]#

Transaction: TransactionMultiple SQL statements, either executed at the same time, or not executed at the same timeA transaction is a set of atomic (SELECT) query statements, and multiple queries are treated as a separate unit of workAcid testing:

MySQL based on the field of the group query, the same field of data, only one display, if you want to make this field of all the data, display in a row, you can use the Group_contat function in the query, the default data merge with commas, separate6

Working with MySQL database configured master-slave synchronization, but do not know why synchronization failed. Working environment can not be operated casually, I built a master-slave synchronization environment in the local.Backup tool is

After installing MySQL, find MySQL in system references and start it.After startup, enter the MySQL path command in the terminal and add the path to the path:Path= "$PATH":/usr/local/mysql/binThe command to log on to MySQL at the terminal is as

CREATE TABLE ' Zsl_test ' (' ID ' INT (TEN) null DEFAULT NULL,' Class ' INT (TEN) null DEFAULT NULL,' Score ' INT (TEN) null DEFAULT NULL)Collate= ' Utf8_general_ci 'Engine=innodb;INSERT into zsl_test values (1,1,80);INSERT into zsl_test values (2,1,

The method for copying MySQL query results to a new table (update and insert) and mysql query results In MySQL, you can copy the query results to another table. there are usually two types of replication: update existing data and insert a new

The sorting method of group_concat () function in MySQL, mysqlgroup_concat The parameters of the group_concat () function can be directly sorted by order. 666 .. The following is an example. First, let's look at table t1 below. For example, we

Mysql deletes record statement, mysql deletes record statement For example:Id name value1 a pp2 a pp3 B iii4 B pp5 B pp6 c pp7 c pp8 c iiiId is the primary keyThis result is required.Id name value1 a pp3 B iii4 B pp6 c pp8 c iiiMethod 1Delete

Mysql left join, right join, inner join Usage Analysis, innerjoin The following is an exampleTable A records the following:AID aNum1 a200501112 a200501123 a200501134 a200501145 a20050115Table B records the following:BID bName1 20060324012 20060324023

[High-Performance MYSQL post-read casually] about the transaction isolation level, after mysql readsI. Lock types There are many types of locks in MySQL, including common table locks and row locks, and new Metadata locks. Table locks apply locks to

What are stored procedures and triggers, and stored procedure triggers? The simplest way is to define a series of operations in SQL server. You only need to call them to complete the corresponding operations.==========================================

How to change the default engine of Mysql to Innodb: mysqlinnodb Preface InnoDB and MyISAM are the two most common table types used by many people when using MySQL. The two table types have their own advantages and disadvantages, depending on the

Mysql 5.6.24 installation instance tutorial, mysql5.6.24 Preparations before installation: 1) edit the PATH vim /etc/profilePATH=/home/mysql/bin:/home/mysql/lib:$PATHexport PATH 2) Effective PATH source /etc/profile 3) EDIT hosts vim /etc/hosts192.16