text MySQL：基本的MySQL指南

Posted 2021-05-01

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MySQL Guide - Basics
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Connect/Disconnect from MySQL Server
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:~ sudo mysqld_safe                 //Turns on MySQL server
:~ mysql -h host -u root -p         //Connects to MySQL server: "no need to specify host on local"
mysql> quit;                        //Disconnects from MySQL
:~ mysqladmin -u root -p shutdown   //Shuts down MySQL server
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General commands
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mysql> SHOW DATABASES;              //Shows databases for current user
mysql> CREATE DATABASE testDB;      //Creates new database called testDB
mysql> USE testDB;                  //Changes database
mysql> SHOW TABLES;                 //Shows all tables in the current database
mysql> DESCRIBE costumer;           //Displays table information
mysql> SELECT * FROM costumer;      //Shows all rows and columns of the "costumer" table
mysql> SELECT DATABASE();           //Shows current database
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mysql> CREATE TABLE test_table (                    //Creates a...
    -> id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,  //new...
    -> title VARCHAR(128) NOT NULL,                 //table...
    -> text TEXT NOT NULL,                          //with the...
    -> date DATE NOT NULL,                          //specified column names...
    -> author VARCHAR(40)                           //and their data types.
    -> );
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mysql> INSERT INTO test_table (title, text, date, author)	//Inserts a single row to "test_table"
    ->
    -> VALUES ('My title', 'My description', CURRENT_DATE, 'Billy');
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mysql> GRANT ALL ON testDB.* TO 'some_user'@'client_host';	//Grants permissions to a user for "testDB"
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mysql> SELECT user();	//Shows current logged in user
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mysql> SELECT
    -> user()
    -> \c           //Cancels the command
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 SELECT
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mysql> SELECT * FROM costumers WHERE name = 'John';     //Find specific value
mysql> SELECT name FROM costumer;                       //Select a specific column
mysql> SELECT name, lastname FROM costumer;             //Select multiple columns
mysql> SELECT * FROM costumer ORDER BY date;            //Sort rows by the date column
mysql> SELECT DISTINCT name FROM costumer;              //Find only distinct values, no duplicates
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mysql> SELECT * FROM costumer WHERE (news_letter = 'Y') //Select when both conditions are met
    -> AND (order_date >= '2012-01-14');
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mysql> SELECT * FROM costumers WHERE sex='m' AND news_letter='Y'  //Selects when both conditions... 
    -> ORDER BY name DESC;                                        //are met, and sorts in...
                                                                  //descending order by name.
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mysql> SELECT * FROM costumers WHERE sex='m' AND news_letter='Y'    //Select when all 3 conditions...
		-> AND order_date > '2012-01-12' ORDER BY name ASC; //are met, and sorts in ascending...
                                                                    //order by name.
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mysql> SELECT COUNT(*) FROM costumers;                  //Counts numbers of rows in "costumers" table
mysql> SELECT * FROM costumers WHERE name LIKE 'b%';	//Select all names that start with the letter 'b'
mysql> SELECT * FROM costumers WHERE name LIKE '%n';	//Select all names that end with the letter 'h'
mysql> SELECT * FROM costumers WHERE name LIKE '%i%';	//Select all names that contain the letter 'i'
mysql> SELECT * FROM costumers WHERE name LIKE '____';	//Select all names that contain exactly 4 characters
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 ALTER TABLE mytable
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mysql> ALTER TABLE costumer RENAME costumers;		//Rename table to "costumers"
mysql> ALTER TABLE costumer RENAME TO costumers;	//Alternative syntax for the same task  
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mysql> ALTER TABLE costumers CHANGE birth_date birth DATE;    //Rename a column (data type is required)
mysql> ALTER TABLE costumers MODIFY order_date DATE NOT NULL; //Modify a column's data type to... DATE NOT NULL
mysql> ALTER TABLE costumers ADD age INT;                     //Add a new column as integer type
mysql> ALTER TABLE costumers DROP COLUMN ip;                  //Remove an entire column
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 UPDATE mytable
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mysql> UPDATE costumers SET news_letter='Y' WHERE name='Billy'; //Change column's value if condition is met
mysql> UPDATE costumer SET sex='m', news_letter='N' WHERE name='Billy'; //Change multiple column values... 
                                                                        //when condition is met.
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mysql> UPDATE costumers SET age=YEAR(CURDATE()) - YEAR(birth_date); 

//Set the age column on each row with SQL functions YEAR() and CURDATE()
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 DELETE FROM mytable  ->  'this would delete everything'
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mysql> DELETE FROM costumers WHERE id=4;	//Remove the 4th row in the table
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