mysql uses all columns of the query table

start command

sudo service mysqld start

stop order

sudo service mysqld stop

Check if the MySQL service is running:

sudo systemctl status mysql

Use the command to check whether it is started

ps -ef|grep mysqld

Use the command to connect

mysql -u -p passwd

Enter the password according to the prompt to enter the mysql command line.

View the number of databases: 

show databases;

View the number of a database table :

SELECT count(TABLE_NAME) FROM information_schema.TABLES WHERE TABLE_SCHEMA='database name';

View the specified database size:

SELECT sum(DATA_LENGTH)+sum(INDEX_LENGTH) FROM information_schema.TABLES where TABLE_SCHEMA='数据库名';

The result obtained is in bytes

New database command:

 create database database name;

Backup database command :

mysqldump -u root -p database name> 2015.9.21.sql;

Import a large SQL file command to the database:

source + file path/file name

In the MySQL database:

Query all column names of a table in a database

SELECT COLUMN_NAME FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA = 'db_name' AND TABLE_NAME = 'tb_name';

Query all column names of a table in a database and connect them with commas

SELECT GROUP_CONCAT(COLUMN_NAME SEPARATOR ",") FROM information_schema.COLUMNS 
WHERE TABLE_SCHEMA = 'db_name' AND TABLE_NAME = 'tb_name';

Note: only need to replace db_name (database name) and tb_name (table name)