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mysql技术内幕sampdb_MySql技术内幕之MySQL入门(1)

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MySql技術內幕之MySQL入門(1)

安裝

檢查系統中是否已經安裝了MySQL

sudo netstat -tap | grep mysql

若沒有顯示已安裝結果，則沒有安裝。否則表示已經安裝。

sudo apt-get install mysql-server mysql-client

安裝過程中會讓輸入密碼，記得把密碼記住。

關于注釋

三種寫法：

用#單行注釋

用-- 單行注釋，注意后面有一空格

/* */ 多行注釋

mysql> SELECT 1+1; # 這個注釋直到該行結束

mysql> SELECT 1+1; -- 這個注釋直到該行結束

mysql> SELECT 1 /* 這是一個在行中間的注釋 */ + 1;

mysql> SELECT 1+

這是一個

多行注釋的形式

執行SQL語句

ltq@lab:~$ mysql -u root -p

Enter password:

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 7

Server version: 5.7.19-0ubuntu0.16.04.1 (Ubuntu)

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SELECT NOW(); # 查詢當前日期和時間，使用分號終止語句

+---------------------+

| NOW() |

+---------------------+

| 2017-10-20 22:07:14 |

+---------------------+

1 row in set (0.00 sec)

mysql> SELECT NOW()\g # 查詢當前日期和時間，使用\g終止語句

+---------------------+

| NOW() |

+---------------------+

| 2017-10-20 22:07:56 |

+---------------------+

1 row in set (0.00 sec)

mysql> SELECT NOW(), USER(), VERSION()\g # 查詢時間，用戶，系統版本，并在一列展示

+---------------------+----------------+-------------------------+

| NOW() | USER() | VERSION() |

+---------------------+----------------+-------------------------+

| 2017-10-20 22:08:28 | root@localhost | 5.7.19-0ubuntu0.16.04.1 |

+---------------------+----------------+-------------------------+

1 row in set (0.00 sec)

mysql> SELECT NOW(), USER(), VERSION()\G #查詢時間，用戶，系統版本，并在一行展示

*************************** 1. row ***************************

NOW(): 2017-10-20 22:08:43

USER(): root@localhost

VERSION(): 5.7.19-0ubuntu0.16.04.1

1 row in set (0.00 sec)

mysql> SELECT NOW(),

-> USER(),

-> VERSION()\G # 在多行輸入

*************************** 1. row ***************************

NOW(): 2017-10-20 22:18:44

USER(): root@localhost

VERSION(): 5.7.19-0ubuntu0.16.04.1

1 row in set (0.00 sec)

mysql> SELECT NOW(),

-> USER(),

-> \c # 使用\c表示不執行上述語句

mysql> SELECT NOW(); SELECT USER(); SELECT VERSION(); # 在一行輸入多條語句

+---------------------+

| NOW() |

+---------------------+

| 2017-10-20 22:21:38 |

+---------------------+

1 row in set (0.00 sec)

+----------------+

| USER() |

+----------------+

| root@localhost |

+----------------+

1 row in set (0.00 sec)

+-------------------------+

| VERSION() |

+-------------------------+

| 5.7.19-0ubuntu0.16.04.1 |

+-------------------------+

1 row in set (0.00 sec)

關于命令大小寫

一般用大寫字母表示SQL關鍵字和函數名；

用小寫字母表示數據庫，表和列的名字。

創建數據庫

mysql> CREATE DATABASE sampdb; # 創建數據庫

Query OK, 1 row affected (0.00 sec)

mysql> SELECT DATABASE(); # 查看當前數據庫，結果為NULL

+------------+

| DATABASE() |

+------------+

| NULL |

+------------+

1 row in set (0.00 sec)

mysql> USE sampdb; # 把sampdb設置為當前默認選擇的數據庫

Database changed

mysql> SELECT DATABASE(); # 查看當前數據庫，結果為NULL

+------------+

| DATABASE() |

+------------+

| sampdb |

+------------+

1 row in set (0.00 sec)

mysql> source create_president.sql # 如果已經在終端cd到create_president.sql路徑下，那么則可運行該語句

Query OK, 0 rows affected (0.15 sec)

Query OK, 0 rows affected (0.23 sec)

補充，文件create_president.sql的內容如下：

# Create president table for U.S. Historical League

DROP TABLE IF EXISTS president;

#@ _CREATE_TABLE_

CREATE TABLE president

(

last_name VARCHAR(15) NOT NULL,

first_name VARCHAR(15) NOT NULL,

suffix VARCHAR(5) NULL,

city VARCHAR(20) NOT NULL,

state VARCHAR(2) NOT NULL,

birth DATE NOT NULL,

death DATE NULL

);

#@ _CREATE_TABLE_

查看表的信息

mysql> DESCRIBE president; # 查看president表的結構

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

7 rows in set (0.00 sec)

mysql> DESC president; # DESCRIBE的簡寫為DESC

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

7 rows in set (0.00 sec)

mysql> EXPLAIN president;

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

7 rows in set (0.00 sec)

mysql> SHOW COLUMNS FROM president;

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

7 rows in set (0.00 sec)

mysql> SHOW FIELDS FROM president;

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

7 rows in set (0.00 sec)

查看更加詳細的信息

mysql> SHOW FULL COLUMNS FROM president; # SHOW FULL COLUMNS 比 SHOW COLUMNS顯示更多的信息

+------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+

+------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+

+------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+

7 rows in set (0.00 sec)

查看與給定模式相匹配的列

如果需要對所查找的信息加以限定，

mysql> DESCRIBE president '%name'; # 查找名稱中包含name的項

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

2 rows in set (0.00 sec)

mysql> SHOW FIELDS FROM president like '%name'; # 查找名稱中包含name的項，另外一種寫法

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

+------------+-------------+------+-----+---------+-------+

2 rows in set (0.00 sec)

插入數據

利用insert添加行

一次添加一行數據：

INSERT INTO president VALUES ('Washington','George',NULL,'Wakefield','VA','1732-02-22','1799-12-14');

INSERT INTO president VALUES ('Adams','John',NULL,'Braintree','MA','1735-10-30','1826-07-04');

一次添加多行數據：

INSERT INTO president VALUES ('Jefferson','Thomas',NULL,'Albemarle County','VA','1743-04-13','1826-07-04'), ('Madison','James',NULL,'Port Conway','VA','1751-03-16','1836-06-28');

利用文件添加新行

mysql> source insert_president.sql

Query OK, 0 rows affected (0.00 sec)

Query OK, 1 row affected (0.06 sec)