1. Connect to Mysql
Format: mysql -h host address -u username -p user password
1. Connect to MYSQL on this machine.
First open a DOS window, then enter the directory mysqlbin, and then type the command mysql -u root -p. After pressing Enter, you will be prompted to enter your password. Note that the user name can have spaces or no spaces in front of it, but there must be no spaces in front of the password, otherwise you will be Please re-enter password.
If MYSQL has just been installed, the super user root does not have a password, so just press Enter to enter MYSQL. The MYSQL prompt is: mysql>
2. Connect to MYSQL on the remote host. Assume that the IP of the remote host is: 110.110.110.110, the user name is root, and the password is abcd123. Then type the following command:
mysql -h110.110.110.110 -u root -p 123; (Note: There is no need to add a space between u and root, and the same is true for others)
3. Exit the MYSQL command: exit (Enter)
2. Change the password
Format: mysqladmin -u username -p old password password new password
1. Add a password ab12 to root.
First enter the directory mysqlbin under DOS, and then type the following command
Mysqladmin -u root -password ab12
Note: Because root does not have a password at the beginning, the -p old password item can be omitted.
2. Change the root password to djg345.
Mysqladmin -u root -p ab12 password djg345
3. Add a new user
Note: Different from the above, the following is a command in the MYSQL environment, so it is followed by a semicolon as the command terminator
Format: grant select on database.* to username@login host identified by "password"
1. Add a user test1 with the password abc, so that he can log in on any host and query, insert, modify, and delete all databases permission. First connect to MYSQL as the root user, and then type the following command:
grant select,insert,update,delete on *.* to [email=test1@”%]test1@”%[/email]” Identified by “abc”;
But adding more users is very dangerous. If someone knows the password of test1, then he can log in to your mysql database on any computer on the Internet and do whatever he wants with your data. Solution See 2.
2. Add a user test2 with the password abc so that he can only log in on localhost and perform query, insert, modify and delete operations on the database mydb (localhost refers to the local host, where the MYSQL database is located) that host), so even if the user knows the password of test2, he cannot directly access the database from the Internet, and can only access it 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 don’t want test2 to have a password, you can type 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 database
Note: You must connect to the Mysql server before creating the database
Command: create database
Example 1: Create a database named xhkdb
mysql> create database xhkdb;
Example 2: Create a database and assign users
①CREATE DATABASE Database name;
②GRANT SELECT,INSERT,UPDATE,DELETE ,CREATE,DROP,ALTER ON database name.* TO database name@localhost IDENTIFIED BY 'password';
③SET PASSWORD FOR 'database name'@'localhost' = OLD_PASSWORD('password');
Execute 3 commands in sequence Complete the database creation. Note: The Chinese "password" and "database" need to be set by the user.
4.2 Show databases
Command: show databases (note: there is an s at the end)
mysql> show databases;
Note: In order to no longer display garbled characters, the default encoding of the database must be modified. The following takes the GBK encoding page as an example:
1. Modify the MYSQL configuration file: modify default-character-set=gbk in my.ini
2. Modify when the code is running:
①Java code: jdbc:mysql:// localhost:3306/test?useUnicode=true&characterEncoding=gbk
②PHP code: header("Content-Type:text/html;charset=gb2312");
③C 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. The concatenated collation becomes the default collation for the character set. This function works similarly to the SET NAMES statement, but it also sets the value of mysql- > charset, thereby affecting the character set set by mysql_real_escape_string().
4.3 Delete database
Command: drop database
For example: delete a database named 0 rows affected (0.00 sec)
Example 2: Delete a database that does not exist
mysql> drop database drop_database;
ERROR 1008 (HY000): Can't drop database 'drop_database'; database doesn't exist
// // An error occurred. The 'drop_database' database cannot be dropped. The database does not exist.
mysql> drop database if exists drop_database;
Query OK, 0 rows affected, 1 warning (0.00 sec)//Generate a warning indicating that this 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 Determine whether the database exists, no error will be generated if it does not exist
Query OK, 0 rows affected (0.00 sec)
4.4 Connect to the database
Command: use
For example: If the xhkdb database exists, try to access it:
mysql> use xhkdb;
Screen prompt: Database changed
The use statement can notify MySQL to use the db_name database as the default (current) database for subsequent statements. . This database remains the default database until the end of the segment, or until a different USE statement is issued:
mysql> USE db1;
mysql> SELECT COUNT(*) FROM mytable; # selects from db1.mytable
mysql> USE db2 ;
mysql> SELECT COUNT(*) FROM mytable; # selects from db2.mytable
Use the USE statement to mark a specific current database, which will not prevent you from accessing tables in other databases. The following example can access the author table from the db1 database and the edit 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;
USE statement is set up for compatibility with Sybase.
Some netizens asked how to exit after connecting. 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 other databases, just use
use other database names
.
4.5 Currently selected database
Command: mysql> select database();
The SELECT command in MySQL is similar to print or write in other programming languages. You can use it to display the results of a string, number, mathematical expression, etc. How to use the special features of the SELECT command in MySQL?
1. Display the version of MYSQL
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 string
mysql> SELECT "welecome to my blog!";
+----------------------+
| welcome to my blog! |
+----------------------+
| welcome to my blog! |
+---------- ------------+
1 row in set (0.00 sec)
5. When used as a calculator
select ((4 * 4) / 10 ) + 25;
+----- ------------------+
| ((4 * 4) / 10 ) + 25 |
+---------------- ------+
| 26.60 |
+----------------------+
1 row in set (0.00 sec)
6. String Connect string
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 here to concatenate strings. In addition, we also used the AS we learned before to give the result column 'CONCAT(f_name, " ", l_name)' a pseudonym.
5.1 Create a data table
Command: create table
( [,.. ]);
For example, create a table named MyClass,
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 data tableCommand: drop table
For example: delete table named MyClass table
mysql> drop table MyClass;
DROP TABLE is used to drop one or more tables. You must have DROP permission on each table. All table data and table definitions will be canceled, so be careful when using this statement!
Note: For a partitioned table, DROP TABLE will permanently cancel the table definition, cancel each partition, and cancel all data stored in these partitions. DROP TABLE also cancels the partition definition (.par) file associated with the dropped table.
For tables that do not exist, use IF EXISTS to prevent errors. When using IF EXISTS, a NOTE is generated for each table that does not exist.
RESTRICT and CASCADE can make partitioning easier. Currently, RESTRICT and CASCADE don't work.
5.4 Insert data into table
Command: insert into
[( [,.. ])] values (value 1)[, (value n)]
For example: to Insert two records into the table MyClass. These two records indicate that the score of Tom numbered 1 is 96.45, Joan numbered 2 has a score of 82.99, and Wang numbered 3 has a score of 96.5.
mysql> insert into MyClass values(1,'Tom',96.45),(2,'Joan',82.99), (2,'Wang', 96.59);
Note: insert into can only be inserted into the table each time Insert a record. 5.5 Query the data in the table
1), query all rows
Command: select from where
For example: View all data in the table MyClass
mysql> select * from MyClass;
2), query the first few rows of data
For example: view the first 2 rows of data in the table MyClass
mysql> select * from MyClass order by id limit 0,2;
select is generally used in conjunction with where to query more precise and complex data.
5.6 Delete data in the table
Command: delete from table name where expression
For example: delete the record numbered 1 in the table MyClass
mysql> delete from MyClass where id=1;
The following is a before and after deletion of data Table comparison.
The following is an example of PHP code to delete all records with LastName='Griffin' 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);
?>Copy after login
After this deletion, the table looks like this:
5.7 Modify the table Medium data
Syntax: update table name set field = new value,... where condition
mysql> update MyClass set name='Mary' where id=1;
Example 1: Single table MySQL UPDATE statement:
UPDATE [LOW_PRIORITY ] [IGNORE] tbl_name SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE where_definition] [ORDER BY ...] [LIMIT row_count]
Example 2: UPDATE statement for multiple tables:
UPDATE [LOW_PRIORITY] [ IGNORE] table_references SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE where_definition]
UPDATE syntax can update each column in the original table row with a new value. The SET clause indicates which columns are to be modified and which values are to be given. The WHERE clause specifies which rows should be updated. If there is no WHERE clause, all rows are updated. If the ORDER BY clause is specified, rows are updated in the order specified. The LIMIT clause is used to give a limit to the number of rows that can be updated.
5.8 Add fields
Command: alter table table name add field type other;
For example: a field passtest is added to the table MyClass, the type is int(4), the default value is 0
mysql> alter table MyClass add passtest int(4) default '0'
Add index
mysql> alter table table name add index index name (field name 1[, field name 2...]);
Example: mysql> alter table employee add index emp_name ( name);
Add primary key index
mysql> alter table table name add primary key (field name);
Example: mysql> alter table employee add primary key(id);
Add unique restriction index
mysql> alter table table name add unique index name (field name);
Example: mysql> alter table employee add unique emp_name2(cardnumber);
Delete an index
mysql> alter table table name drop index index name;
Example : mysql>alter table employee drop index emp_name;
Add a 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 a 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: change the name of table MyClass to YouClass
mysql> rename table MyClass to YouClass;
When you execute RENAME, you cannot have any locked tables or active transactions. You must also have ALTER and DROP permissions on the original table, and CREATE and INSERT permissions on the new table.
If MySQL encounters any errors during multi-table renaming, it will perform a backward renaming of all renamed tables, returning everything to its original state.
RENAME TABLE was added in MySQL 3.23.23.
6. Back up database
The command is executed in the [url=file://\mysql\bin]\mysql\bin[/url] directory of DOS
1. Export the entire database
The export file is stored in the mysqlbin 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 username -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 library 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 An example of creating a database and a table 1
drop database if exists school; //If SCHOOL exists, delete it
create database school; //Create the library SCHOOL
use school; //Open the library SCHOOL
create table teacher // Create 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
//The following are the insertion fields
insert into teacher values(”,'allen','Dalian No. 1 Middle School','1976-10-10′);
insert into teacher values(",'jack','Dalian No. 2 Middle School' ,'1975-12-23′);
If you type the above command at the mysql prompt, it will work, but it is not convenient for debugging.
1. You can write the above command as it is into a text file, assuming it is school.sql, then copy it to c:\, and enter the directory [url=file://\mysql\bin]\mysql in DOS state \bin[/url], and then type the following command:
mysql -uroot -p password If successful, leave a blank line and nothing will be displayed; if there is an error, there will be a prompt. (The above command has been debugged, you only need to remove the // comment to use it).
2. Or use mysql> source c:\school.sql; after entering the command line to import the school.sql file into the database.
7.2 An example of creating a database and a table 2
drop database if exists school; //If SCHOOL exists, delete it
create database school; //Create the library SCHOOL
use school; //Open the library SCHOOL
create table teacher //Create 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
//The following are the insertion fields
insert into teacher values('''',''glchengang'',''Shenzhen No. 1 Middle School'',''1976-10-10'');
insert into teacher values('''',''jack'',''Shenzhen No. 1 Middle School'',''1975-12-23'');
Note: In the table under construction
1. Set the ID to the length A numeric field of 3: int (3); and let each record automatically add one: auto_increment; it cannot be empty: not null; and let it become the main field primary key.
2. Set NAME to a character field of length 10
3. Set ADDRESS to a character field of length 50, and the default value is Shenzhen.
4. Set YEAR as the date field.
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