mysql基本使用
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打开mysql: mysql -hlocalhost -uroot -p密码
接下来就是高能了，有时候会因为mysql版本不同的问题，字段的问题，空格的问题经常造成错误，所以以下的一些代码在你的机器上出错请不要见怪，不懂的就去问百度。
表演开始：
先创建一个列表：
mysql> create table student(
-> stu_id int auto_increment,
-> name CHAR(32) NOT NULL,
-> age INT NOT NULL,
-> register_date date not null,
-> primary key (id));
ERROR 1046 (3D000): No database selected
what?出错了，怎么办，原因是什么
我们要先创建一个数据库
mysql> create database xsphpdb;
Query OK, 1 row affected (0.00 sec)
ok，再这创建一个列表
mysql> create table xsphpdb.users(
-> id int,
-> name char(30),
-> age int,sex char(3));
Query OK, 0 rows affected (0.08 sec)
我们再来看看这个列表
mysql> show tables;
ERROR 1046 (3D000): No database selected
what?又出错了，
因为你虽然创建了一个数据库，却没有进入它，故而出错。
mysql> use xsphpdb;
Database changed
mysql> show tables;
+-------------------+
| Tables_in_xsphpdb |
+-------------------+
| users |
+-------------------+
1 row in set (0.02 sec)
this is ok ,那么我们接下来做什么呢？
查看一个列表的详细信息
mysql> desc users;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | char(30) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
| sex | char(3) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
OK
再来创建一个：
mysql> create table studen(
-> stu_id INT NOT NULL AUTO_INCREMENT,
-> name CHAR(32) NOT NULL,
-> age INT NOT NULL,
-> register_date DATE not null,
-> PRIMARY KEY ( stu_id )
-> );
mysql> desc studen;
+---------------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+----------+------+-----+---------+----------------+
| stu_id | int(11) | NO | PRI | NULL | auto_increment |
| name | char(32) | NO | | NULL | |
| age | int(11) | NO | | NULL | |
| register_date | date | NO | | NULL | |
+---------------+----------+------+-----+---------+----------------+
大家看这个表，跟上面的表有什么区别？
在于NUll
记住以后创建列表一定要加
-> stu_id INT NOT NULL AUTO_INCREMENT,
-> name CHAR(32) NOT NULL,
-> age INT NOT NULL,
-> register_date DATE not null,
not null ，否则你将迎来的是各种错误
插入数据： insert into studen (name,age,register_date) values ("alex li",22,"2016-03-4");
select * from studen;
查看元素
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 1 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
1 row in set (0.00 sec)
如此重复几遍
mysql> select * from studen;
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 1 | alex li | 22 | 2016-03-04 |
| 2 | alex li | 22 | 2016-03-04 |
| 3 | alex li | 22 | 2016-03-04 |
| 4 | alex li | 22 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
| 6 | alex li | 22 | 2016-03-04 |
| 7 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
如何查数据呢
mysql> select * from studen limit 3 offset 2;
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 3 | alex li | 22 | 2016-03-04 |
| 4 | alex li | 22 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
mysql> select * from studen limit 1 offset 2;
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 3 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
mysql> select * from studen where stu_id>3 and age=22;
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 4 | alex li | 22 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
| 6 | alex li | 22 | 2016-03-04 |
| 7 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
4 rows in set (0.00 sec)
此处，还有一个特别的概念：
模糊寻找：
mysql> select * from studen where register_date like "2016-03%";
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 1 | alex li | 22 | 2016-03-04 |
| 2 | alex li | 22 | 2016-03-04 |
| 3 | alex li | 22 | 2016-03-04 |
| 4 | alex li | 22 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
| 6 | alex li | 22 | 2016-03-04 |
| 7 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
7 rows in set, 1 warning (0.00 sec)
增，查，学完了，我们来学习如何修改：
update studen set name="ChenRonghua",age=33 where stu_id=4;
ok
update studen set name="ChenRonghua",age=33 where stu_id>6;
ok
mysql> select * from studen where register_date like "2016-03%";
+--------+-------------+-----+---------------+
| stu_id | name | age | register_date |
+--------+-------------+-----+---------------+
| 1 | alex li | 22 | 2016-03-04 |
| 2 | alex li | 22 | 2016-03-04 |
| 3 | alex li | 22 | 2016-03-04 |
| 4 | ChenRonghua | 33 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
| 6 | alex li | 22 | 2016-03-04 |
| 7 | ChenRonghua | 33 | 2016-03-04 |
+--------+-------------+-----+---------------+
最后一个是删
delete from studen where name="ChenRonghua"；
还有一个就是如何排序的问题
正着排序，与反着排序
mysql> select * from studen order by stu_id;
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 1 | alex li | 22 | 2016-03-04 |
| 2 | alex li | 22 | 2016-03-04 |
| 3 | alex li | 22 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
| 6 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
5 rows in set (0.00 sec)
mysql> select * from studen order by stu_id desc;
+--------+---------+-----+---------------+
| stu_id | name | age | register_date |
+--------+---------+-----+---------------+
| 6 | alex li | 22 | 2016-03-04 |
| 5 | alex li | 22 | 2016-03-04 |
| 3 | alex li | 22 | 2016-03-04 |
| 2 | alex li | 22 | 2016-03-04 |
| 1 | alex li | 22 | 2016-03-04 |
+--------+---------+-----+---------------+
再添加两个数据
mysql> insert into studen (name,age,register_date) values ("wngd",23,"2016-06-4");
Query OK, 1 row affected (0.00 sec)
mysql> insert into studen (name,age,register_date) values ("wn45",2324,"2016-07-4");
Query OK, 1 row affected (0.00 sec)
mysql> select * from studen;
+--------+---------+------+---------------+
| stu_id | name | age | register_date |
+--------+---------+------+---------------+
| 1 | alex li | 22 | 2016-03-04 |
| 2 | alex li | 22 | 2016-03-04 |
| 3 | alex li | 22 | 2016-05-31 |
| 5 | alex li | 22 | 2016-03-04 |
| 6 | alex li | 22 | 2016-03-04 |
| 8 | wngd | 23 | 2016-06-04 |
| 9 | wn45 | 2324 | 2016-07-04 |
+--------+---------+------+---------------+
7 rows in set (0.00 sec)
对数据进行统计
mysql> select name,count(*) as stu_num from studen group by register_date;
+---------+---------+
| name | stu_num |
+---------+---------+
| alex li | 4 |
| alex li | 1 |
| wngd | 1 |
| wn45 | 1 |
+---------+---------+
4 rows in set (0.00 sec)
mysql> select name,sum(age) from studen;
+---------+----------+
| name | sum(age) |
+---------+----------+
| alex li | 2457 |
+---------+----------+
1 row in set (0.00 sec)
求总和
mysql> select name,sum(age) from studen group by name;
+---------+----------+
| name | sum(age) |
+---------+----------+
| alex li | 110 |
| wn45 | 2324 |
| wngd | 23 |
+---------+----------+
mysql> select name,sum(age) from studen group by name with rollup;
+---------+----------+
| name | sum(age) |
+---------+----------+
| alex li | 110 |
| wn45 | 2324 |
| wngd | 23 |
| NULL | 2457 |
+---------+----------+
4 rows in set (0.00 sec)
mysql> select coalesce(name,"total age"),sum(age) from studen group by name with rollup;
+----------------------------+----------+
| coalesce(name,"total age") | sum(age) |
+----------------------------+----------+
| alex li | 110 |
| wn45 | 2324 |
| wngd | 23 |
| total age | 2457 |
+----------------------------+----------+
再给大家介绍一下：
mysql> ALTER TABLE studen ADD zk_en VARCHAR(16) not null; #加一列一定要加not null,否则以后的操作很难办，由于版本不同，各解决方法也不尽相同
Query OK, 0 rows affected (0.07 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc studen;
+---------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+---------------+------+-----+---------+----------------+
| stu_id | int(11) | NO | PRI | NULL | auto_increment |
| name | char(32) | NO | | NULL | |
| age | int(11) | NO | | NULL | |
| register_date | date | NO | | NULL | |
| sex | enum('M','F') | YES | | NULL | |
| phone | int(11) | NO | | NULL | |
| zk_env | varchar(16) | YES | | NULL | |
| zk_en | varchar(16) | NO | | NULL | |
+---------------+---------------+------+-----+---------+----------------+
mysql> alter table studen change zk_en gender char(32) not null default "X";#修改类型
Query OK, 7 rows affected (0.07 sec)
Records: 7 Duplicates: 0 Warnings: 0
mysql> desc studen;
+---------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+---------------+------+-----+---------+----------------+
| stu_id | int(11) | NO | PRI | NULL | auto_increment |
| name | char(32) | NO | | NULL | |
| age | int(11) | NO | | NULL | |
| register_date | date | NO | | NULL | |
| sex | enum('M','F') | YES | | NULL | |
| phone | int(11) | NO | | NULL | |
| zk_env | varchar(16) | YES | | NULL | |
| gender | char(32) | NO | | X | |
+---------------+---------------+------+-----+---------+----------------+
但是，如果还是不够怎么办呢
我们学习怎么把zk_env null改变呢
update studen set zk_ens=0 where zk_ens is null;
alter table studen MODIFY COLUMN zk_ens int(11) NOT NULL DEFAULT '0' ;this is ok
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