打開終端輸入如下命令:
/usr/local/MySQL/bin/mysql -u root -p
其中root為用戶名。
這時會出現如下命令:
Enter password:
此時如果你沒有改密碼,直接敲回車。否則,輸入你的密碼。
這樣就可以訪問你的數據庫服務器了。
數據表的基
1.1 create 創建數據庫
create database firstDB;
1.2 show 查看所有數據庫
mysql> show databases;+--------------------+ Database +--------------------+ information_schema firstDB mysql performance_schema +--------------------+rows in set (0.00 sec)
1.3 alter 修改數據庫
alter 命令修改數據庫編碼:
默認創建的數據庫默認不支持中文字符,如果我們需要它支持中文字符,則將它的編碼設置為utf8格式:
mysql> ALTER DATABASE testDB CHARACTER SET UTF8;Query OK, 1 row affected (0.00 sec)
1.4 use 使用數據庫
mysql> use firstDB;Database changed
1.5 查看當前使用的數據庫
mysql> select database();+------------+ database() +------------+ firstdb +------------+1 row in set (0.00 sec)
1.6 drop 刪除數據庫
mysql> drop database firstDB;Query OK, 0 rows affected (0.00 sec)
我們首先創建一個數據庫,提供我們往后的使用:
mysql> create database testDB;Query OK, 1 row affected (0.00 sec)
創建后記得用use命令進入(使用)數據庫,不然后面的操作都會不成功的。
2.1 create 創建表
mysql> create table PEOPLE ( -> ID int AUTO_INCREMENT PRIMARY KEY, -> NAME varchar(20) not null, -> AGE int not null, -> BIRTHDAY datetime); Query OK, 0 rows affected (0.01 sec)
2.2 show 顯示表
顯示當前數據庫所有的數據表
mysql> show tables;+------------------+ Tables_in_testdb +------------------+ PEOPLE +------------------+1 row in set (0.00 sec)
2.3 desc 查看表結構
mysql> desc PEOPLE -> ;+----------+-------------+------+-----+---------+----------------+ Field Type Null Key Default Extra +----------+-------------+------+-----+---------+----------------+ ID int(11) NO PRI NULL auto_increment NAME varchar(20) NO NULL AGE int(11) NO NULL BIRTHDAY datetime YES NULL +----------+-------------+------+-----+---------+----------------+4 rows in set (0.01 sec)
2.4 alter 修改表結構(增、刪、改)
默認創建的表不支持中文字符,所以需將表編碼設置為utf8:
mysql> ALTER TABLE KEYCHAIN CONVERT TO CHARACTER SET UTF8;Query OK, 1 row affected (0.02 sec)Records: 1 Duplicates: 0 Warnings: 0
2.4.1 insert 在表中添加列(字段)
mysql> alter table PEOPLE add star BOOL;Query OK, 0 rows affected (0.02 sec)Records: 0 Duplicates: 0 Warnings: 0
提示:在MySQL里,布爾類型會自動轉換為tinyint(1)類型。
我們不妨使用desc去查看一下PEOPLE表結構:
mysql> desc PEOPLE;+----------+-------------+------+-----+---------+----------------+ Field Type Null Key Default Extra +----------+-------------+------+-----+---------+----------------+ ID int(11) NO PRI NULL auto_increment NAME varchar(20) NO NULL AGE int(11) NO NULL BIRTHDAY datetime YES NULL star tinyint(1) YES NULL +----------+-------------+------+-----+---------+----------------+5 rows in set (0.00 sec)
現在,你該相信我了吧?
2.4.2 alter 修改表(列)字段
mysql> alter table PEOPLE MODIFY star int;Query OK, 0 rows affected (0.01 sec)Records: 0 Duplicates: 0 Warnings: 0
也可以指定 int(n) 的長度,比如 int(2)。
我們再次使用desc查看PEOPLE表結構:
mysql> desc PEOPLE;+----------+-------------+------+-----+---------+----------------+ Field Type Null Key Default Extra +----------+-------------+------+-----+---------+----------------+ ID int(11) NO PRI NULL auto_increment NAME varchar(20) NO NULL AGE int(11) NO NULL BIRTHDAY datetime YES NULL star int(11) YES NULL +----------+-------------+------+-----+---------+----------------+5 rows in set (0.00 sec)
2.4.3 delete 刪除表(列)字段
mysql> alter table PEOPLE DROP column star;Query OK, 0 rows affected (0.02 sec)Records: 0 Duplicates: 0 Warnings: 0
刪除后,再次查看PEOPLE表結構:
mysql> desc PEOPLE;+----------+-------------+------+-----+---------+----------------+ Field Type Null Key Default Extra +----------+-------------+------+-----+---------+----------------+ ID int(11) NO PRI NULL auto_increment NAME varchar(20) NO NULL AGE int(11) NO NULL BIRTHDAY datetime YES NULL +----------+-------------+------+-----+---------+----------------+4 rows in set (0.00 sec)
刪除字段成功,現在我們已經不能看到star的字段了。
2.4.4 rename 重命名表名
mysql> RENAME TABLE PEOPLE TO NEW_PEOPLE;Query OK, 0 rows affected (0.00 sec)
2.4.5 null or not null
修改表字段允許為空或不允許為空:
mysql> ALTER TABLE PEOPLE MODIFY AGE INT(3) NULL;Query OK, 0 rows affected (0.01 sec)Records: 0 Duplicates: 0 Warnings: 0
把 PEOPLE 表的 AGE 字段設置成“允許為空”,即插入記錄時這個字段可以不錄入。否則相反。
它的格式為:ALTER TABLE MODIFY
mysql> create table newTable select * from PEOPLE;Query OK, 0 rows affected (0.01 sec)Records: 0 Duplicates: 0 Warnings: 0
我們查看一下目前數據庫存在的表:
mysql> show tables;+------------------+ Tables_in_testdb +------------------+ PEOPLE newTable +------------------+2 rows in set (0.00 sec)
本操作,包含增、刪、改、查數據。
以下命令均在PEOPLE表上操作。
3.1 增加數據(增)
PEOPLE表目前是沒有數據的,它是空的數據表,我們現在先添加一些數據。
insert into 命令添加數據:
mysql> insert into PEOPLE VALUES (null, 'Anny', 22, '1992-05-22');Query OK, 1 row affected (0.00 sec)
使用select命令查看表(會在后面介紹),現在我們查看PEOPLE數據表的數據:
mysql> select * from PEOPLE;+----+------+-----+---------------------+ ID NAME AGE BIRTHDAY +----+------+-----+---------------------+ 1 Anny 22 1992-05-22 00:00:00 +----+------+-----+---------------------+1 row in set (0.00 sec)
數據表現在有一條數據。
我們多添加幾條數據,如:
mysql> select * from PEOPLE;+----+--------+-----+---------------------+ ID NAME AGE BIRTHDAY +----+--------+-----+---------------------+ 1 Anny 22 1992-05-22 00:00:00 2 Garvey 23 1991-05-22 00:00:00 3 Lisa 25 1989-05-22 00:00:00 4 Nick 24 1990-05-22 00:00:00 5 Rick 24 1991-05-22 00:00:00 +----+--------+-----+---------------------+5 rows in set (0.00 sec)
3.2 刪除數據(刪)
delete 命令刪除數據:
mysql> delete from PEOPLE where name = 'Lisa';Query OK, 1 row affected (0.01 sec)
再次查詢PEOPLE表:
mysql> select * from PEOPLE;+----+--------+-----+---------------------+ ID NAME AGE BIRTHDAY +----+--------+-----+---------------------+ 1 Anny 22 1992-05-22 00:00:00 2 Garvey 23 1991-05-22 00:00:00 4 Nick 24 1990-05-22 00:00:00 5 Rick 24 1991-05-22 00:00:00 +----+--------+-----+---------------------+4 rows in set (0.00 sec)
已經看不到名為“Lisa”的數據了。
3.3 修改數據(改)
update 命令修改數據:
mysql> update PEOPLE set name='Calvin' where name = 'Garvey';Query OK, 1 row affected (0.00 sec)Rows matched: 1 Changed: 1 Warnings: 0
查詢PEOPLE表內容:
mysql> select * from PEOPLE;+----+--------+-----+---------------------+ ID NAME AGE BIRTHDAY +----+--------+-----+---------------------+ 1 Anny 22 1992-05-22 00:00:00 2 Calvin 23 1991-05-22 00:00:00 4 Nick 24 1990-05-22 00:00:00 5 Rick 24 1991-05-22 00:00:00 +----+--------+-----+---------------------+4 rows in set (0.00 sec)
名為“Garvey”的記錄已經修改為“Calvin”。
3.4 查詢數據(查)
select 命令查詢數據,最簡單的就是查詢表的所有數據,也就是我們最初使用到的那條命令:
mysql> select * from PEOPLE;+----+--------+-----+---------------------+ ID NAME AGE BIRTHDAY +----+--------+-----+---------------------+ 1 Anny 22 1992-05-22 00:00:00 2 Calvin 23 1991-05-22 00:00:00 4 Nick 24 1990-05-22 00:00:00 5 Rick 24 1991-05-22 00:00:00 +----+--------+-----+---------------------+4 rows in set (0.00 sec)
格式:select * from <表名>,*代表所有字段。
查詢數據時也可指定顯示的(列)字段:
mysql> select NAME, AGE, BIRTHDAY from PEOPLE;+--------+-----+---------------------+ NAME AGE BIRTHDAY +--------+-----+---------------------+ Anny 22 1992-05-22 00:00:00 Calvin 23 1991-05-22 00:00:00 Nick 24 1990-05-22 00:00:00 Rick 24 1991-05-22 00:00:00 +--------+-----+---------------------+4 rows in set (0.00 sec)
格式:select <字段名,字段名,…> from <表名>。
select查詢命令還有很多的高級用法,比如用來查找不重復(distinct)的數據,使數據按條件排序(order by),按查詢條件顯示數據(where)等等。這些都會在下一篇文章作重點介紹,請大家繼續留意我的博客,謝謝。
4.1 創建視圖
視圖是從數據庫里導出一個或多個表的虛擬表,是用來方便用戶對數據的操作。
mysql> CREATE VIEW PEOPLE_VIEW ( -> NAME, AGE) -> AS SELECT NAME, AGE FROM PEOPLE;
創建成功后查看視圖。
PEOPLE PEOPLE.AGE PEOPLE.BIRTHDAY PEOPLE.ID PEOPLE.NAME mysql> SELECT * FROM PEOPLE_VIEW -> ;+--------+-----+ NAME AGE +--------+-----+ Anny 22 Calvin 23 Nick 24 Rick 24 +--------+-----+4 rows in set (0.00 sec)
我們也可以使用 DESC 命令查看視圖的結構。
mysql> DESC PEOPLE_VIEW;+-------+---------+------+-----+---------+-------+ Field Type Null Key Default Extra +-------+---------+------+-----+---------+-------+ ID int(11) NO 0 +-------+---------+------+-----+---------+-------+1 row in set (0.01 sec)
4.2 替換視圖
創建或替換原有視圖。
mysql> CREATE OR REPLACE VIEW PEOPLE_VIEW(PEOPLE_ID,PEOPLE_NAME,PEOPLE_AGE) AS SELECT ID,NAME,AGE FROM PEOPLE;Query OK, 0 rows affected (0.00 sec)
創建或替換后查看視圖。
mysql> SELECT * FROM PEOPLE_VIEW;+-----------+-------------+------------+ PEOPLE_ID PEOPLE_NAME PEOPLE_AGE +-----------+-------------+------------+ 1 Anny 22 2 Calvin 23 4 Nick 24 5 Rick 24 +-----------+-------------+------------+4 rows in set (0.00 sec)
4.3 操作視圖
當視圖數據有變化時(增、刪、改),真實的表數據也會隨著改變。也就是說,對視圖的操作就是對表的數據,所以我們可以把視圖當作表。
例:往視圖插入一條數據。
mysql> INSERT INTO PEOPLE_VIEW VALUES(NULL, 'Kerry', '33');Query OK, 1 row affected (0.00 sec)
插入數據成功后查看視圖。
mysql> SELECT * FROM PEOPLE_VIEW ;+-----------+-------------+------------+ PEOPLE_ID PEOPLE_NAME PEOPLE_AGE +-----------+-------------+------------+ 1 Anny 22 2 Calvin 23 4 Nick 24 5 Rick 24 6 Kerry 33 +-----------+-------------+------------+5 rows in set (0.00 sec)
可以在視圖上看到我們剛剛插入的數據,現在我們就來驗證一下真實的表是否也會作出變化。
mysql> SELECT * FROM PEOPLE;+----+--------+-----+---------------------+ ID NAME AGE BIRTHDAY +----+--------+-----+---------------------+ 1 Anny 22 1992-05-22 00:00:00 2 Calvin 23 1991-05-22 00:00:00 4 Nick 24 1990-05-22 00:00:00 5 Rick 24 1991-05-22 00:00:00 6 Kerry 33 NULL +----+--------+-----+---------------------+5 rows in set (0.00 sec)
可見,真實的表數據也已經有所改變,剛剛往視圖里插入的那一條數據存在于真實表中,真理便是:對視圖的操作就是對表的數據。
4.4 刪除視圖
mysql> DROP VIEW PEOPLE_VIEW;Query OK, 0 rows affected (0.00 sec)
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