MySQL

1. Check if MySQL service is installed in the current Linux environment: sudo services MySQL start2. Install MySQL server, core program: sudo apt-get install Mysql-server3. Install the MySQL client: sudo apt-get install mysql-client4. End of

Date and time data types Date 3 bytes, dates, format: 2014-09-18 time 3 bytes, duration, format: 08:42:30datetime 8 bytes, date time, format:2014-09-18 08:42:30timestamp 4 bytes, automatic storage record modified time year 1 bytes, yearsNumeric data

Knowledge Background:MySQL the default value of the maximum number of connections is 100, for a large number of concurrent connections of the database, when the connection request is greater than the default number of connections, there will be no

Using indexes for sortingKEY A_b_c (a,b,c)Order by can use the index leftmost prefix-orderby a-order by a,b-order by A,C-order by a desc,b desc,c descIf where the leftmost prefix of the index is defined as a constant, the order by can use the

http://repo.mysql.com/yum/1. Newly opened cloud server, need to detect whether the system comes with the installation of MySQL# Yum List Installed | grep MySQL2. If you find a system that comes with MySQL, do it decisively# yum-y Remove mysql-libs.x8

Char is a kind 固定长度 of type,VarChar is a kind 可变长度 of type,The difference between them is:char (m) Type of data column, each value occupies M bytes, if a length of less than M,mysql will be on its right with a space character to complement. (The

single loop inserts multiple dataDELIMITER;;CREATE PROCEDURETest_insert ()BEGIN DECLAREYint DEFAULT 1; whileY - DoInsert intoSCHOOL_SP_MJ (School_id,mojor_id,status)Values(1Y1); SETY=Y+1; END while ; Commit; END;;//can be here first to detect

What's the only thing?1. All values of the indexed column (field) can only occur once, i.e. must be unique--------------------------------------------------------------------------------The difference between a primary key index and a unique index1.

Backing Up the database#mysqldump database name > database backup name #mysqldump -a-u user name-p password database name > database backup name #mysqldump1. Export structure does not export data2. Export data does not export structure3. Export Data

Service MySQL start times: error! The server quit without updating PID file (/usr/local/mysql/data/mysql1.pid), error.1. Check the error log:Could not open or create the system tablespace. If you tried to add new data files to the system tablespace,

After using the VPS for a period of time, you find that the disk space is almost full. My VPS bought a 500GB disk at the time of purchase, and the provider presented a 20GB high-performance system disk. So the system has two disk space. The database

1. Open terminal, enter: CD ~Will enter the ~ folder2. Then enter: Touch. Bash_profileAfter the carriage return is executed,2. Re-enter: Open-e. bash_profileThis file is opened in TextEdit (this should be a blank document if the environment variable

Install MySQL stepsYum install mysql-server installing the MySQL clientYum Install Mysql-server installation Server sideYum Install Mysql-devel installation Server sideMySQL configuration file/etc/my.cnf add Default-character-set=utf8 character Set

Bo Master Original, reproduced annotated Source:In the MySQL application, the scope of the query is a lot of time range as a condition for the scope of query, time range query hasMany kinds of writing, first summed up the Between....and ... How to

Error-no operations allowed after connection closed. org.hibernate.exception.jdbcconnectionexception:could not Execute Queryat Org.hibernate.exception.SQLStateConverter.convert (sqlstateconverter.java:74) at

Create a new table:CREATE TABLE ' tree ' ( ' id ' int (one) not NULL auto_increment COMMENT ' primary key ', ' parent_id ' int (one) ' NOT null, ' name ' varchar (ten) not NULL, PRIMARY KEY (' id ')) engine=innodb DEFAULT Charset=utf8;　　Create

MySQL version 5.7Database connection Version mysql mysql-connector-java 6.0.6Link stringJdbc.driver=com.mysql.cj.jdbc.driverjdbc.url=jdbc:mysql://localhost:3306/usercenterdb?characterencoding=utf8&useunicode=true&

querying the entire contents of a data tableMysql> Show tables, #查看当前数据库下的全部表 +--------------------+| Tables_in_ceshi_ku |+--------------------+| Biao | | Ceshi_biao |+--------------------+2 rows in Set (0.00 sec) mysql> select

First, MySQL master-slave synchronization (for the back to achieve read and write separation, MMM high-availability cluster basis)Main Library configuration: IP address of the main library: 192.168.4.1111, first to the user authorization, used to

DB2 to MySQL, DB2 to MySQL I will not talk nonsense, and directly go to the topic... >. The data type is generally used. The principle of the data type to be modified is to increase the scope in a small range, which is easy to understand and will