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
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)
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。
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。