Detailed description of Mysql commands (recommended) and mysql commands

Detailed description of Mysql commands (recommended) and mysql commands

This section describes commonly used MySQL commands, including connecting to the database, changing the password, managing users, operating databases, operating data tables, and database backup. Each Command is provided with instance instructions, making it easier to understand.

1. Connect to Mysql

Format: mysql-h host address-u user name-p User Password

1. Connect to MYSQL on the local machine.

First, open the DOS window, enter the mysql \ bin directory, type the mysql-u root-p command, and press enter to prompt you to enter the password. note that there can be spaces or spaces before the user name, but there must be no spaces before the password. Otherwise, you can re-enter the password.

If you have just installed MYSQL, the Super User root has no password, so press enter to enter MYSQL. The MYSQL prompt is: mysql>

2. Connect to MYSQL on the remote host. Assume that the IP address of the remote host is 110.110.110.110, the user name is root, and the password is abcd123. Enter the following command:

Mysql-h110.110.110.110-u root-p 123)

3. exit MYSQL command: exit (Press ENTER)

2. Change the password

Format: mysqladmin-u username-p old password New password

1. Add a password ab12 to the root user.

First, enter the mysql \ bin directory under DOS, and then type the following command

mysqladmin -u root -password ab12

Note: because the root account does not have a password at the beginning, the old-p password can be omitted.

2. Change the root password to djg345.

mysqladmin -u root -p ab12 password djg345

3. Add new users

Note: Unlike the above, the following commands in the MYSQL environment are followed by a semicolon as the command Terminator.

Format: grant select on database. * to username @ login host identified by "password"

1. Add a user named "test1" with the password "abc" so that he can log on to any host and have the permission to query, insert, modify, and delete all databases. First, use the root user to connect to MYSQL, and then type the following command:

grant select,insert,update,delete on *.* to [email=test1@”%]test1@”%[/email]” Identified by “abc”;

However, the added users are very dangerous. If someone knows the password of test1, then he can log on to your mysql database on any computer on the internet and do whatever he wants for your data. See solution 2.

2. Add a user named "test2" with the password "abc" so that the user can only log on to localhost and query, insert, modify, and delete the database mydb (localhost refers to the local host, that is, the host where the MYSQL database is located. In this way, the user knows the password of test2, and cannot directly access the database from the internet, but can only access the database through the web page on the MYSQL host.

 grant select,insert,update,delete on mydb.* to [email=test2@localhost]test2@localhost[/email] identified by “abc”;

If you do not want test2 to have a password, you can run another command to remove the password.

 grant select,insert,update,delete on mydb.* to [email=test2@localhost]test2@localhost[/email] identified by “”;

4.1 create a database

Note: before creating a database, connect to the Mysql server.

Command: create database <database Name>

Example 1: Create a database named xhkdb

 mysql> create database xhkdb;

Example 2: Create a database and assign users

① Create database name;

② Grant select, INSERT, UPDATE, DELETE, CREATE, DROP, alter on database name. * TO database name @ localhost identified by 'Password ';

③ Set password for 'database name' @ 'localhost' = OLD_PASSWORD ('Password ');

Execute three commands in sequence to create a database. Note: You must set the Chinese "password" and "Database.

4.2 Display Database

Command: show databases (Note: The last s is available)

mysql> show databases;

Note: In order to stop displaying garbled characters, you need to modify the default database encoding. The following uses the GBK encoding page as an example:

1. Modify the MYSQL configuration file: Modify default-character-set = gbk in my. ini

2. modify the code during running:

① Java code: jdbc: mysql: // localhost: 3306/test? UseUnicode = true & characterEncoding = gbk

② PHP code: header ("Content-Type: text/html; charset = gb2312 ");

③ C language code: int mysql_set_character_set (MYSQL * mysql, char * csname );

This function is used to set the default character set for the current connection. The string csname specifies a valid Character Set Name. Connection proofreader is used as the default proofreader for character sets. This function works in a similar way as the set names statement, but it can also SET the value of mysql-> charset, thus affecting the character SET by mysql_real_escape_string.

4.3 Delete A Database

Command: drop database <database Name>

For example, delete a database named xhkdb.

mysql> drop database xhkdb;

Example 1: delete a database that already exists

  mysql> drop database drop_database;  Query OK, 0 rows affected (0.00 sec)

Example 2: delete an uncertain Database

Mysql> drop database drop_database; ERROR 1008 (HY000): Can't drop database 'drop _ database'; database doesn' t exist // an ERROR occurs, the 'drop _ database' database cannot be deleted. The database does not exist. Mysql> drop database if exists drop_database; Query OK, 0 rows affected, 1 warning (0.00 sec) // generates a warning indicating that the database does not exist mysql> create database drop_database; Query OK, 1 row affected (0.00 sec) mysql> drop database if exists drop_database; // if exists determines whether the database exists and does not exist, there is no error Query OK, 0 rows affected (0.00 sec)

4.4 connect to the database

Command: use <Database Name>

For example, if the xhkdb database exists, try to access it:

mysql> use xhkdb;

On-screen prompt: Database changed

The use statement can notify MySQL to use the db_name database as the default (current) database for subsequent statements. The database remains the default database until the end of the CIDR block or until a different USE statement is published:

  mysql> USE db1;  mysql> SELECT COUNT(*) FROM mytable;  # selects from db1.mytable  mysql> USE db2;  mysql> SELECT COUNT(*) FROM mytable;  # selects from db2.mytable

Using the USE statement to mark a specific current database does not prevent you from accessing tables in other databases. The following example shows how to access the author table from the db1 database and edit the table from the db2 database:

  mysql> USE db1;  mysql> SELECT author_name,editor_name FROM author,db2.editor    ->    WHERE author.editor_id = db2.editor.editor_id;

The USE statement is set up to be compatible with Sybase.

Some netizens asked how to exit after the connection. In fact, you don't need to exit. After using the database, you can use show databases to query all databases. If you want to jump to another database, use

Use other database names

You can.

4.5 currently selected Database

Command:

mysql> select database();

The SELECT command in MySQL is similar to the print or write command in other programming languages. You can use it to display the results of a string, number, and mathematical expression. How to use the special features of the SELECT command in MySQL?

1. Display MYSQL version

mysql> select version(); +-----------------------+ | version()       | +-----------------------+ | 6.0.4-alpha-community | +-----------------------+ 1 row in set (0.02 sec)

2. display the current time

mysql> select now(); +---------------------+ | now()        | +---------------------+ | 2009-09-15 22:35:32 | +---------------------+ 1 row in set (0.04 sec)

3. Display year, month, and day

SELECT DAYOFMONTH(CURRENT_DATE); +--------------------------+ | DAYOFMONTH(CURRENT_DATE) | +--------------------------+ |            15 | +--------------------------+ 1 row in set (0.01 sec)  SELECT MONTH(CURRENT_DATE); +---------------------+ | MONTH(CURRENT_DATE) | +---------------------+ |          9 | +---------------------+ 1 row in set (0.00 sec)  SELECT YEAR(CURRENT_DATE); +--------------------+ | YEAR(CURRENT_DATE) | +--------------------+ |        2009 | +--------------------+ 1 row in set (0.00 sec)

4. Display strings

mysql> SELECT "welecome to my blog!"; +----------------------+ | welecome to my blog! | +----------------------+ | welecome to my blog! | +----------------------+ 1 row in set (0.00 sec)

5. When using a calculator

select ((4 * 4) / 10 ) + 25; +----------------------+ | ((4 * 4) / 10 ) + 25 | +----------------------+ |        26.60 | +----------------------+ 1 row in set (0.00 sec)

6. String concatenation

select CONCAT(f_name, " ", l_name) AS Name from employee_data where title = 'Marketing Executive'; +---------------+ | Name     | +---------------+ | Monica Sehgal | | Hal Simlai  | | Joseph Irvine | +---------------+ 3 rows in set (0.00 sec) 

Note: The CONCAT () function is used to concatenate strings. In addition, we also use the previously learned AS to give the result column 'concat (f_name, "", l_name) 'A Kana.

5.1 create a data table

Command: create table <table Name> (<field name 1> <type 1> [,... <field name n> <type n>]);

For example, to create a table named MyClass,

Field name	Numeric type	Data width	Empty or not	Primary Key?	Auto-Increment	Default Value
Id	Int	4	No	Primary key	Auto_increment
Name	Char	20	No
Sex	Int	4	No			0
Degree	Double	16	Yes

mysql> create table MyClass(> id int(4) not null primary key auto_increment,> name char(20) not null,> sex int(4) not null default '0',> degree double(16,2));

5.3 delete a data table

Command: drop table <table Name>

For example, delete a table named MyClass.

  mysql> drop table MyClass;

Drop table is used to cancel one or more tables. You must have the DROP permission for each table. All table data and table definitions will be canceled, so be careful when using this statement!

Note: For a TABLE with partitions, drop table permanently cancels TABLE definitions, cancels partitions, and removes all data stored in these partitions. Drop table also cancels the partition definition (. par) file associated with the canceled TABLE.

For tables that do not exist, use if exists to prevent errors. When if exists is used, a NOTE is generated for each table that does not exist.

RESTRICT and CASCADE make partitioning easier. Currently, RESTRICT and CASCADE do not work.

5.4 insert data into a table

Command: insert into <Table Name> [(<field name 1> [,... <field name n>])] values (value 1) [, (value n)]

For example, insert two records into the MyClass table. The two records indicate that the result of Tom numbered 1 is 96.45, and the result of Joan numbered 2 is 82.99, wang, numbered 3, scored 96.5.

 mysql> insert into MyClass values(1,'Tom',96.45),(2,'Joan',82.99), (2,'Wang', 96.59);

Note: insert into can only insert one record into the table at a time.

5.5 query table data

1) query all rows

Command: select <Field 1, Field 2,...> from <Table Name> where <expression>

For example, you can view all data in the MyClass table.

  mysql> select * from MyClass;

2) query the first few rows of data

For example, view the first two rows of data in the MyClass table.

mysql> select * from MyClass order by id limit 0,2;

Select is generally used with where to query more precise and complex data.

5.6 Delete table data

Command: delete from table name where expression

For example, delete the record numbered 1 in MyClass.

mysql> delete from MyClass where id=1;

The following is a comparison between tables before and after data deletion.

The following uses the PHP code as an example to delete all LastName = 'grigin' records in the "Persons" table:

<?php   $con = mysql_connect("localhost","peter","abc123");   if (!$con)   {   die('Could not connect: ' . mysql_error());   }   mysql_select_db("my_db", $con);   mysql_query("DELETE FROM Persons WHERE LastName='Griffin'"); mysql_close($con); ?>

After this deletion, the table is like this.

FirstName	LastName	Age
Glenn	Quagmire	33

5.7 Modify Table Data

Syntax: update table name set field = new value ,... Where condition

mysql> update MyClass set name='Mary' where id=1;

Example 1: MySQL UPDATE statement for a single table:

UPDATE [LOW_PRIORITY] [IGNORE] tbl_name SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE where_definition] [ORDER BY ...] [LIMIT row_count]

Example 2: UPDATE statements for multiple tables:

UPDATE [LOW_PRIORITY] [IGNORE] table_references SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE where_definition]

The UPDATE syntax uses the new value to UPDATE columns in the original table rows. The SET clause indicates the columns to be modified and the values to be given. The WHERE clause specifies the rows to be updated. If there is no WHERE clause, all rows are updated. If the order by clause is specified, the row is updated in the specified ORDER. The LIMIT clause is used to specify a LIMIT to LIMIT the number of rows that can be updated.

5.8 Add a field

Command: alter table name, add, other field types;

For example, a passtest field is added to the MyClass table. The type is int (4) and the default value is 0.

mysql> alter table MyClass add passtest int(4) default '0'

Add Index

Mysql> alter table name add index name (field name 1 [, field name 2…]);

Example:

mysql> alter table employee add index emp_name (name);

Index with primary keywords

Mysql> alter table name add primary key (field name );

Example:

mysql> alter table employee add primary key(id);

Add an index with unique conditions

Mysql> alter table name add unique index name (field name );

Example:

mysql> alter table employee add unique emp_name2(cardnumber);

Delete An index

Mysql> alter table Name drop index name;

Example:

mysql>alter table employee drop index emp_name;

Add field:

mysql> ALTER TABLE table_name ADD field_name field_type;

Modify the original field name and type:

mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

Delete field:

MySQL ALTER TABLE table_name DROP field_name;

5.9 Modify Table Name

Command: rename table original table name to new table name;

For example, the MyClass name in the table is changed to YouClass.

 mysql> rename table MyClass to YouClass;

When you execute RENAME, you cannot have any locked table or activity transactions. You must also have the ALTER and DROP permissions for the original table and the CREATE and INSERT permissions for the new table.

If MySQL encounters any error in renaming multiple tables, it will rename all renamed tables and return everything to the initial state.

Rename table is added to MySQL 3.23.23.

6. Back up the database

The command is executed in the DOS [url = file: // \ mysql \ bin] \ mysql \ bin [/url] Directory.

1. Export the entire database

The exported files are stored in the mysql \ bin directory by default.

Mysqldump-u username-p Database Name> exported file name

  mysqldump -u user_name -p123456 database_name > outfile_name.sql

2. Export a table

Mysqldump-u user name-p database name Table Name> exported file name

  mysqldump -u user_name -p database_name table_name > outfile_name.sql

3. Export a database structure

mysqldump -u user_name -p -d –add-drop-table database_name > outfile_name.sql

-D no data-add-drop-table add a drop table before each create statement

4. Export with language Parameters

mysqldump -uroot -p –default-character-set=latin1 –set-charset=gbk –skip-opt database_name > outfile_name.sql

For example, back up the aaa database to the file back_aaa:

[root@test1 root]# cd　/home/data/mysql　　[root@test1 mysql]# mysqldump -u root -p --opt aaa > back_aaa

7.1 Example 1 of a database and table Creation

Drop database if exists school; // if SCHOOL exists, delete create database school; // create a database SCHOOLuse school; // open the database SCHOOLcreate table teacher // create the table TEACHER (id int (3) auto_increment not null primary key, name char (10) not null, address varchar (50) default 'shenzhen ', year date); // The end of table creation // insert into teacher values (", 'allen', 'dalian Zhongyi ', '2017-10-10'); insert into teacher values (", 'jack', 'dalian No. 2 Middle East', '2017-12-23 ′);

If you type the preceding command at the mysql prompt, debugging is not convenient.

1. You can write the above commands into a text file as they are, for example, school. SQL, then copy it to c :\\, and enter the directory [url = file: // \ mysql \ bin] \ mysql \ bin [/url], and then type the following command:

Mysql-uroot-p password <c: \ school. SQL

If it succeeds, no display is displayed for a blank row. If there is an error, a prompt is displayed. (The preceding command has been debugged. You only need to remove the // annotation to use it ).

2. You can use mysql> source c: \ school. SQL after entering the command line. You can also import the school. SQL file to the database.

7.2 an instance of database creation and table creation 2

Drop database if exists school; // if SCHOOL exists, delete create database school; // create a database SCHOOLuse school; // open the database SCHOOLcreate table teacher // create the table TEACHER (id int (3) auto_increment not null primary key, name char (10) not null, address varchar (50) default ''shenzhen '', year date); // end of table creation // insert into teacher values (''', ''glchengang '', ''shenzhen No. 1 middle ''', ''2010-10-10 ''); insert into teacher values (''', ''jack'', ''shenzhen No. 1 middle '', ''1975-12-23 '');

Note: Table Creation

1. Set the ID to a numeric field with a length of 3: int (3), and enable it to automatically add auto_increment for each record; it cannot be blank: not null; in addition, set the primary key as the primary key.

2. Set NAME to a 10-character field

3. Set ADDRESS to a 50-character field, and the default value is Shenzhen.

4. Set YEAR as the date field.

The above is all the content of this article. I hope it will be helpful for your learning and support for helping customers.