注意:MySQL数据库命令不区分大小写。但在MAC的终端,如果你想使用tab自动补全命令,那么你就必须使用大写,这样MAC的终端才会帮你补全命令,否则你按N遍tab都不会有响应。
1、数据库(database)管理
1.1、create创建数据库
create database firstDB;
1.2、show查看所有数据库
mysql> show databases;+--------------------+| Database |+--------------------+| information_schema || firstDB || mysql || performance_schema |+--------------------+4 rows in set (0.00 sec)
1.3、alter修改数据库
alter命令修改数据库编码:
默认创建的数据库默认不支持中文字符,如果我们需要它支持中文字符,则将它的编码设置为utf8格式:
mysql> ALTER DATABASE testDB CHARACTER SET UTF8;Query OK, 1 row affected (0.00 sec)
1.4、use使用数据库
mysql> use firstDB;Database changed
1.5、查看当前使用的数据库
mysql> select database();+------------+| database() |+------------+| firstdb |+------------+1 row in set (0.00 sec)
1.6、drop删除数据库
mysql> drop database firstDB;Query OK, 0 rows affected (0.00 sec)
2、数据表(table)管理
我们首先创建一个数据库,提供我们往后的使用:
mysql> create database testDB;Query OK, 1 row affected (0.00 sec)
创建后记得用use命令进入(使用)数据库,不然后面的操作都会不成功的。
2.1、create创建表
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显示表
显示当前数据库所有的数据表
mysql> show tables;+------------------+| Tables_in_testdb |+------------------+| PEOPLE |+------------------+1 row in set (0.00 sec)
2.3、desc查看表结构
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修改表结构(增、删、改)
默认创建的表不支持中文字符,所以需将表编码设置为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,布尔类型会自动转换为tinyint(1)类型。
我们不妨使用desc去查看一下PEOPLE表结构:
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)
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)的长度,比如int(2)。
我们再次使用desc查看PEOPLE表结构:
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删除表(列)字段
mysql> alter table PEOPLE DROP column star;Query OK, 0 rows affected (0.02 sec)Records: 0 Duplicates: 0 Warnings: 0
删除后,再次查看PEOPLE表结构:
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)
删除字段成功,现在我们已经不能看到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
修改表字段允许为空或不允许为空:
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字段设置成“允许为空”,即插入记录时这个字段可以不录入。否则相反。
它的格式为:ALTER TABLE <TALBE_NAME> MODIFY <CLOUMN> <NULL 'OR' NOT NULL>
2.5、create利用已有数据创建新表
mysql> create table newTable select * from PEOPLE;Query OK, 0 rows affected (0.01 sec)Records: 0 Duplicates: 0 Warnings: 0
我们查看一下目前数据库存在的表:
mysql> show tables;+------------------+| Tables_in_testdb |+------------------+| PEOPLE || newTable |+------------------+2 rows in set (0.00 sec)
3、数据的操作及管理
数据表的基本操作,包含增、删、改、查数据。
以下命令均在PEOPLE表上操作。
3.1、增加数据(增)
PEOPLE表目前是没有数据的,它是空的数据表,我们现在先添加一些数据。
insert into命令添加数据:
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(会在后面介绍),现在我们查看PEOPLE数据表的数据:
mysql> select * from PEOPLE;+----+------+-----+---------------------+| ID | NAME | AGE | BIRTHDAY |+----+------+-----+---------------------+| 1 | Anny | 22 | 1992-05-22 00:00:00 |+----+------+-----+---------------------+1 row in set (0.00 sec)
数据表现在有一条数据。
我们多添加几条数据,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、删除数据(删)
delete命令删除数据:
mysql> delete from PEOPLE where name = 'Lisa';Query OK, 1 row affected (0.01 sec)
再次查询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)
已经看不到名为“Lisa”的数据了。
3.3、修改数据(改)
update命令修改数据:
mysql> update PEOPLE set name='Calvin' where name = 'Garvey';Query OK, 1 row affected (0.00 sec)Rows matched: 1 Changed: 1 Warnings: 0
查询PEOPLE表内容:
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)
名为“Garvey”的记录已经修改为“Calvin”。
3.4 查询数据(查)
select命令查询数据,最简单的就是查询表的所有数据,也就是我们最初使用到的那条命令:
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。
查询数据时也可指定显示的(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查询命令还有很多的高级用法,比如用来查找不重复(distinct)的数据,使数据按条件排序(order by),按查询条件显示数据(where)等等。这些都会在下一篇文章作重点介绍,请大家继续留意我的博客,谢谢。
4、管理视图
创建视图
视图是从数据库里导出一个或多个表的虚拟表,是用来方便用户对数据的操作。
mysql> CREATE VIEW PEOPLE_VIEW (-> NAME, AGE)-> AS SELECT NAME, AGE FROM PEOPLE;
创建成功后查看视图。
PEOPLEPEOPLE.AGEPEOPLE.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)
我们也可以使用DESC命令查看视图的结构。
mysql> DESC PEOPLE_VIEW;+-------+---------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+-------+---------+------+-----+---------+-------+| ID | int(11) | NO || 0 | |+-------+---------+------+-----+---------+-------+1 row in set (0.01 sec)
替换视图
创建或替换原有视图。
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)
创建或替换后查看视图。
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)
操作视图
当视图数据有变化时(增、删、改),真实的表数据也会随着改变。也就是说,对视图的操作就是对表的数据,所以我们可以把视图当作表。
例:往视图插入一条数据。
mysql> INSERT INTO PEOPLE_VIEW VALUES(NULL, 'Kerry', '33');Query OK, 1 row affected (0.00 sec)
插入数据成功后查看视图。
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)
可以在视图上看到我们刚刚插入的数据,现在我们就来验证一下真实的表是否也会作出变化。
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)
可见,真实的表数据也已经有所改变,刚刚往视图里插入的那一条数据存在于真实表中,真理便是:对视图的操作就是对表的数据。
删除视图
mysql> DROP VIEW PEOPLE_VIEW;Query OK, 0 rows affected (0.00 sec)
参考:
/GarveyCalvin/p/4297282.html