MySQL

Common commandsPrinciple: Use the tool as much as possible with the visualizer, and the command line is limited to troubleshooting.mysql -u ACCOUNT -pPWD -h IP -P port [-D database] //连接数据库show databases; //显示数据库列表use db_name; //使用数据库show tables;

Table operation of the data 1. Create a tableSyntax: CREATE TABLE table_name (column_name column_type);CREATE TABLE student, ID int not NULL auto_increment, name CHAR (+) NOT NULL,--age INT not NU LL, register_data DATE, PRIMARY KEY

The main purpose of the design index is to help us get the results of the query quickly, whereas a like query starting with% cannot use the B-tree index.Considering that the InnoDB tables are clustered tables (similar to the Index organization table

Test environment centos7.3+mysql5.7A table using the InnoDB engine, the table name Innodb_testThe other table uses the MyISAM engine, and the table name Innodb_testIn the event of a transactional operation, see what happens.Table structure same as

Haha can only blame oneself too food haIt's not long since I contacted this MySQL.Mysql-u root-p when landing MySQL with a terminal todayAnd then you want to see your own database.I use the MySQL client is navicat for MySQL I look at the client

1) Download the required#cd/data/soft# wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-5.7.21.tar.gz# TAR-XFZF Mysql-5.7.21.tar.gzversion 5.7 needs to download a boost C + + 1.59.0, (slow download)# wget

Download the Unzip installation package1. Initialize the database and execute the command in the bin directory of the MySQL installation directory: Execute command mysqld--initialize--consoleA temporary password was generated:

we typically run into a business scenario like this:b host and C database in the same intranet, a host cannot directly access the C database, we can build the agent on the B host let a access C database, we use Haproxy to do this thingCENTOS7

First, start with a new Java project:Then create a package in SRC and set up a test class for testing:Then import MySQL:Once the import is successful, it will appear in the project list:Then start writing code in test:Package com.nf;Import

With SQL statements, delete duplicates only keep oneIn thousands of records, there are some same records, how can you use SQL statements, delete duplicates1, look for redundant records in the table, duplicate records are based on a single field

Modify field arrangement position ALTER table name MODIFY field name 1 data type first| After field name 2 Parameter Description First, optional parameters Change Field 1 to the first field in the table. After field name 2 Insert Field 1 to the back

Multi-table query, SQL JOINS1. INNER JOIN inside joinsSelect S.name as student_name,t.name as Teacher_name from students as s inner joins teachers as T on S.teacherid=t.tid; /*2 table take intersection, inner connection */2. Cross-ConnectSELECT *

InnoDBInnoDB is the default transactional storage engine for MySQL, and only consider using other storage engines if you need to InnoDB unsupported features.The MVCC is used to support high concurrency, and 4 standard isolation mechanisms are

In the development in order to make development more convenient, in the local configuration environment, you want to have direct access to the MySQL database on the server, more convenient management database,You need to remotely connect to the

The first step is to download the JDBC driver jarThe second step is to add the jar path in the test plan (if the drive jar is placed in the path. \apache-jmeter\lib directory, you can eliminate the step of adding a path)Step three, add the JDBC

MyISAM Storage EngineAdvantages: Supports up to 256TB of storage space Read data faster and consume less resources MyISAM Engine Storage File: TBL_NAME.FRM: Table-style definition Tbl_name. MYD: Data files Tbl_name.

1 General IndexALTER TABLE ADD INDEX index_name ('column')2 PRIMARY Key indexALTER TABLE ADD PRIMARY KEY ('column3 Unique IndexesALTER TABLE ADD UNIQUE ('columnA unique index here guarantees uniqueness of the data record, and in many cases, creating

INSERT into ' material ' (' id ', ' file_url ')SELECT id,ekm. ' File_url 'From ' extmaterial ' as EKMLeft JOIN (SELECT ' file_url ' from ' material ' WHERE ' id ' = ID) as PM on PM. ' File_url ' = EKM. ' File_url 'WHERE EKM. ' ext_id ' = Extid and

: http://www.lua.org/download.htmlInstallation method:Execute the following command in turn:Curl-r-O Http://www.lua.org/ftp/lua-5.3.1.tar. gz tar zxf lua-5.3.1.tar. GZ CD lua-5.3.1 make linux test Problems that may

When MySQL is installed, it is only locally connected by default.Mysql-u Root-p MySQL>Use mysql; MySQL>Select 'Host'From user where user='Root'; MySQL>update User Set host ='%'where user ='Root'; MySQL>flush privileges; MySQL>Select 'Host'From user