转载-MySQL之终端（Terminal）管理数据库、数据表、数据的基本操作
MySQL有很多的可视化管理工具，比如“mysql-workbench”和“sequel-pro-”。 现在我写MySQL的终端命令操作的文章，是想强化一下自己对于MySQL的理解，总会比使用图形化的理解透彻，因为我本来就比较喜欢写代码。同时写出来这些文章，是想要给大家当个参考，希望也能对大家有所帮助，有所提升，这就是我为什么要写终端操作MySQL的文章了。
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。
create database firstDB;
mysql> show databases;+--------------------+
| Database |
+--------------------+
| information_schema |
| firstDB |
| mysql |
| performance_schema |
+--------------------+
4 rows in set (0.00 sec)
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)
mysql> use firstDB; Database changed
mysql> select database(); +------------+ | database() | +------------+ | firstdb | +------------+ 1 row in set (0.00 sec)
mysql> drop database firstDB; Query OK, 0 rows affected (0.00 sec)
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。
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)
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)
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)
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
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)
现在，你该相信我了吧？
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)
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。
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>
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)
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。
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)
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。
删除多条数据，可以使用“||”符号分隔条件
mysql> delete from PEOPLE where id = 1 || id = 2;
也可以把“||” 换成“or”
mysql> delete from PEOPLE where id = 1 or id = 2;
还可以用where in的方式批量删除数据
mysql> delete from PEOPLE where id in (1, 2);
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”。
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。
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。
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)
