This article brings you a summary of the basic knowledge of mysql. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
1. Startup and Exit
1. Enter MySQL:
Start MySQL Command Line Client (MySQL DOS interface), directly Just enter the password you used during installation. The prompt at this time is: mysql>
or open the terminal and enter the SQL statement:
mysql –uroot –p123
2. Exit MySQL:
quit or exit
2. Library operations
1. Create database
Command: create database For example : Create a database named xhkdb mysql> create database xhkdb;
2. Display all databases
Command: show databases (note: there is an s at the end) mysql> show databases;
3. Delete database Command: drop database For example: delete the database named xhkdb mysql> drop database xhkdb;
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
5. The currently selected (connected) database mysql> select database();
6. The table information contained in the current database: mysql> show tables; ( Note: there is an s at the end
3. Table operation, you should connect to a database before the operation 1. Create table Command: create table
[,..]);
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));
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2. Get table structure command : desc table name, or show columns from table name
mysql> desc MyClass;
mysql> show columns from MyClass;
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3. Delete table Command: drop table
For example: delete the table named MyClass mysql> drop table MyClass;
4. Insert data Command: insert into
[( [,..For example, insert two records into the table MyClass. These two records represent: the score of Tom named No. 1 is 96.45, and the score of Tom No. 2 is 96.45. The score of Joan, numbered 3, is 82.99, and the score of Wang, numbered 3, is 96.5.
mysql> insert into MyClass values(1,'Tom',96.45),(2,'Joan',82.99), (2,'Wang', 96.59);
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5. Query the data in the table 1), Query all rows command : select from < table name> where < expression> For example: view all data in 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;
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;
7, Modify the data in the table: update table name set field = new value,... where condition mysql> update MyClass set name='Mary' where id=1;
8. Add to the table Field: 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'
9. Change the 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; Update field content update table name set field name = new content update table name set field name = replace(field name,'old content','new Content'); Add 4 spaces in front of the article update article set content=concat(' ',content);
4. Introduction to field types 1 ． INT[(M)] type: normal size integer type 2． DOUBLE[(M,D)] [ZEROFILL] type: Normal size (double precision) floating point number type 3. DATE date type: The supported range is 1000-01-01 to 9999-12-31. MySQL displays DATE values in YYYY-MM-DD format, but allows you to use strings or numbers to assign values to DATE columns 4. CHAR(M) type: fixed-length string type. When stored, the right side is always filled with spaces to the specified length 5. BLOB TEXT type, the maximum length is 65535 (2^16-1) characters. 6. VARCHAR type: variable length string type
5. Database backup 1. Export the entire database mysqldump -u username-p --default-character-set= latin1 database name> Exported file name (the default encoding of the database is latin1) mysqldump -u wcnc -p smgp_apps_wcnc > wcnc.sql
2. Export a table mysqldump -u user name -p database name table name> exported file name mysqldump -u wcnc -p smgp_apps_wcnc users> wcnc_users.sql
3. Export a database structure mysqldump -u wcnc -p -d – add-drop-table smgp_apps_wcnc >d:wcnc_db.sql -d No data –add-drop-table Add a drop table before each create statement
4. Import database Commonly used source commands Enter the mysql database console, For example, mysql -u root -p mysql>use database Then use the source command, the following parameters are Script file (such as the .sql used here) mysql>source d:wcnc_db.sql
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This change affects PHP and other app
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Creating a MySQL table using PHP requires the following steps: Connect to the database. Create the database if it does not exist. Select a database. Create table. Execute the query. Close the connection.
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