mysql 笔记。
1，链接数据库 ：mysql -uroot -p
输入密码：********
强调：
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 79 --->客户端的链接ID，记录了mysql服务到目前为止的链接次数；每个新的链接id都会自动加一。
2，创建数据库
mysql> create database test1;
Query OK, 1 row affected (0.03 sec)------->影响行数1
mysql> drop database test1;
Query OK, 0 rows affected (0.07 sec)------>影响行数0，mysql drop语句的影响行数都为0.
3，创建表：
create table tablename(id int(11) not null,name varchar(20) not null);
Query OK, 0 rows affected (0.14 sec) -------->影响行数0.
4，查看表定义：desc tablename;
mysql> desc user;
5,查看表定义（详细信息）；
mysql> show create table user \G; ------------>参数\G ->作用是便于查看内容较长的记录。
6，删除表：
mysql> drop table user;
Query OK, 0 rows affected (0.06 sec)
7，修改表：
1，修改字段-->修改字段类型(modify)
mysql> alter table user modify name varchar(20) not null;
Query OK, 0 rows affected (0.30 sec)
Records: 0 Duplicates: 0 Warnings: 0
2，字段改名,及该字段类型(change)
mysql> alter table user change name ename varchar(30);
Query OK, 0 rows affected (0.32 sec)
Records: 0 Duplicates: 0 Warnings: 0
3，添加字段：
mysql> alter table user add column age int(2) not null;
Query OK, 0 rows affected (0.30 sec)
Records: 0 Duplicates: 0 Warnings: 0
4，删除表字段：
mysql> alter table user drop column age;
Query OK, 0 rows affected (0.29 sec)
Records: 0 Duplicates: 0 Warnings: 0
5，修改字段排列顺序
mysql> alter table user add column sex int(2) after name;
Query OK, 0 rows affected (0.31 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user modify age int(2) after sex;
Query OK, 0 rows affected (0.28 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user modify sex int(2) first;
Query OK, 0 rows affected (0.30 sec)
Records: 0 Duplicates: 0 Warnings: 0
6，更改表名：
mysql> alter table user rename admin;
Query OK, 0 rows affected (0.06 sec)
8，DML语句（主要针对表记录的操作）；
1，插入语句：
mysql> insert into user(id,name) value (1,'wa');
Query OK, 1 row affected (0.05 sec)
mysql> insert into user values(2,'ho');
Query OK, 1 row affected (0.05 sec)
一次性插入多条记录：
mysql> insert into user values(3,'li'),(4,'wa'),(5,'yan');
Query OK, 3 rows affected (0.05 sec)
Records: 3 Duplicates: 0 Warnings: 0
2，更新语句：
mysql> update user set name = 'hhhhhhhh' where id=1;
Query OK, 1 row affected (0.04 sec)
Rows matched: 1 Changed: 1 Warnings: 0
3，同时更新多个表中的数据
mysql> update emp a,dept b set a.sal=a.sal*b.deptno,b.deptname=a.ename where a.depton=b.depton;
Query OK, 2 rows affected (0.05 sec)
Rows matched: 2 Changed: 2 Warnings: 0
4，删除语句：
mysql> delete from user where id = 2;
Query OK, 1 row affected (0.07 sec)
5，查询语句：
1,普通查询：
select * from user;
select username from user;
2，查询不重复的记录：(distinct);
select distinct deptno from emp;
3,条件查询：
select * from user where id > 20 order by sex desc(降序)|asc(升序);
4,select * from user where depno = 5 order by sex desc | asc limit 10,20; --10 从第十条开始，显示20条记录。
5，select * from user where id > 200 GROUP BY sex WITH ROLLUP HAVING condition
HAVING 和width 区别：
having是对聚合都的结果进行条件过滤，而where 是聚合前就对记录进行过滤，如果逻辑允许，尽量进行where过滤，减少聚合率，提高效率。
6，select sum(sal),max(sal),min(sal) from user;
7,表链接：内链接和外链接
区别：内链接选出两张两张表中互相匹配的记录，外链接则选出其他不匹配的记录。
select ename,deptname from emp,dept where emp.depno = dept.depno;
内链接：左链接，右链接
左链接：包含所有的左边表中的记录，甚至是右边表中没有和他匹配的记录。
右链接：包含所有的右边表中的记录，甚至是左边表中没有和他匹配的记录。
mysql> select * from dept;
+--------+----------+
| depton | deptname |
+--------+----------+
| 1 | spider |
| 2 | java |
| 3 | plat |
+--------+----------+
3 rows in set (0.00 sec)
mysql> select * from emp;
+-------------+----------+-----+--------+
| ename | hiredate | sal | depton |
+-------------+----------+-----+--------+
| wanghongli | 20 | 0 | 1 |
| masongzhao | 30 | 2 | 2 |
| wubinjie | 30 | 3 | 2 |
| jiajinsong | 30 | 2 | 2 |
| lihuailiang | 30 | 3 | 2 |
+-------------+----------+-----+--------+
mysql> select ename,deptname from dept left join emp on dept.depton = emp.depton;
+-------------+----------+
| ename | deptname |
+-------------+----------+
| wanghongli | spider |
| masongzhao | java |
| wubinjie | java |
| jiajinsong | java |
| lihuailiang | java |
| NULL | plat |
+-------------+----------+
mysql> select ename,deptname from emp left join dept on dept.depton=emp.depton;
+-------------+----------+
| ename | deptname |
+-------------+----------+
| wanghongli | spider |
| masongzhao | java |
| wubinjie | java |
| jiajinsong | java |
| lihuailiang | java |
+-------------+----------+
8，子查寻(in,not in,=,!=,exists,not exists);
select * from emp where depton in (select depton from dept);
9，select 1+4;
10 ，常用函数：
mysql> select VERSION();
+-------------------------+
| VERSION() |
+-------------------------+
| 5.5.29-0ubuntu0.12.04.2 |
+-------------------------+
1 row in set (0.00 sec)
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| test1 |
+------------+
1 row in set (0.00 sec)
mysql> SELECT USER();
+----------------+
| USER() |
+----------------+
| root @localhost |
+----------------+
1 row in set (0.00 sec)
11，查看数据库支持的存储引擎：show engines \G;
mysql> show variables like 'have%';
12,索引的设计和使用。
1，myisam和innoDB都支持BTREE索引。默认情况下memory存储引擎支持HASH索引，也支持BTREE索引。mysql支持前缀索引，FULLTEXT索引（全文索引，但是只限于CHAR,VARCHAR,TEXT类型）
2，索引字段必须是非空的。
3，create index[UNIQUE|FULLTEXT|SPATIAL] cityname on city (city(10));
ALTER 添加索引。
1，链接数据库 ：mysql -uroot -p
输入密码：********
强调：
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 79 --->客户端的链接ID，记录了mysql服务到目前为止的链接次数；每个新的链接id都会自动加一。
2，创建数据库
mysql> create database test1;
Query OK, 1 row affected (0.03 sec)------->影响行数1
mysql> drop database test1;
Query OK, 0 rows affected (0.07 sec)------>影响行数0，mysql drop语句的影响行数都为0.
3，创建表：
create table tablename(id int(11) not null,name varchar(20) not null);
Query OK, 0 rows affected (0.14 sec) -------->影响行数0.
4，查看表定义：desc tablename;
mysql> desc user;
5,查看表定义（详细信息）；
mysql> show create table user \G; ------------>参数\G ->作用是便于查看内容较长的记录。
6，删除表：
mysql> drop table user;
Query OK, 0 rows affected (0.06 sec)
7，修改表：
1，修改字段-->修改字段类型(modify)
mysql> alter table user modify name varchar(20) not null;
Query OK, 0 rows affected (0.30 sec)
Records: 0 Duplicates: 0 Warnings: 0
2，字段改名,及该字段类型(change)
mysql> alter table user change name ename varchar(30);
Query OK, 0 rows affected (0.32 sec)
Records: 0 Duplicates: 0 Warnings: 0
3，添加字段：
mysql> alter table user add column age int(2) not null;
Query OK, 0 rows affected (0.30 sec)
Records: 0 Duplicates: 0 Warnings: 0
4，删除表字段：
mysql> alter table user drop column age;
Query OK, 0 rows affected (0.29 sec)
Records: 0 Duplicates: 0 Warnings: 0
5，修改字段排列顺序
mysql> alter table user add column sex int(2) after name;
Query OK, 0 rows affected (0.31 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user modify age int(2) after sex;
Query OK, 0 rows affected (0.28 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user modify sex int(2) first;
Query OK, 0 rows affected (0.30 sec)
Records: 0 Duplicates: 0 Warnings: 0
6，更改表名：
mysql> alter table user rename admin;
Query OK, 0 rows affected (0.06 sec)
8，DML语句（主要针对表记录的操作）；
1，插入语句：
mysql> insert into user(id,name) value (1,'wa');
Query OK, 1 row affected (0.05 sec)
mysql> insert into user values(2,'ho');
Query OK, 1 row affected (0.05 sec)
一次性插入多条记录：
mysql> insert into user values(3,'li'),(4,'wa'),(5,'yan');
Query OK, 3 rows affected (0.05 sec)
Records: 3 Duplicates: 0 Warnings: 0
2，更新语句：
mysql> update user set name = 'hhhhhhhh' where id=1;
Query OK, 1 row affected (0.04 sec)
Rows matched: 1 Changed: 1 Warnings: 0
3，同时更新多个表中的数据
mysql> update emp a,dept b set a.sal=a.sal*b.deptno,b.deptname=a.ename where a.depton=b.depton;
Query OK, 2 rows affected (0.05 sec)
Rows matched: 2 Changed: 2 Warnings: 0
4，删除语句：
mysql> delete from user where id = 2;
Query OK, 1 row affected (0.07 sec)
5，查询语句：
1,普通查询：
select * from user;
select username from user;
2，查询不重复的记录：(distinct);
select distinct deptno from emp;
3,条件查询：
select * from user where id > 20 order by sex desc(降序)|asc(升序);
4,select * from user where depno = 5 order by sex desc | asc limit 10,20; --10 从第十条开始，显示20条记录。
5，select * from user where id > 200 GROUP BY sex WITH ROLLUP HAVING condition
HAVING 和width 区别：
having是对聚合都的结果进行条件过滤，而where 是聚合前就对记录进行过滤，如果逻辑允许，尽量进行where过滤，减少聚合率，提高效率。
6，select sum(sal),max(sal),min(sal) from user;
7,表链接：内链接和外链接
区别：内链接选出两张两张表中互相匹配的记录，外链接则选出其他不匹配的记录。
select ename,deptname from emp,dept where emp.depno = dept.depno;
内链接：左链接，右链接
左链接：包含所有的左边表中的记录，甚至是右边表中没有和他匹配的记录。
右链接：包含所有的右边表中的记录，甚至是左边表中没有和他匹配的记录。
mysql> select * from dept;
+--------+----------+
| depton | deptname |
+--------+----------+
| 1 | spider |
| 2 | java |
| 3 | plat |
+--------+----------+
3 rows in set (0.00 sec)
mysql> select * from emp;
+-------------+----------+-----+--------+
| ename | hiredate | sal | depton |
+-------------+----------+-----+--------+
| wanghongli | 20 | 0 | 1 |
| masongzhao | 30 | 2 | 2 |
| wubinjie | 30 | 3 | 2 |
| jiajinsong | 30 | 2 | 2 |
| lihuailiang | 30 | 3 | 2 |
+-------------+----------+-----+--------+
mysql> select ename,deptname from dept left join emp on dept.depton = emp.depton;
+-------------+----------+
| ename | deptname |
+-------------+----------+
| wanghongli | spider |
| masongzhao | java |
| wubinjie | java |
| jiajinsong | java |
| lihuailiang | java |
| NULL | plat |
+-------------+----------+
mysql> select ename,deptname from emp left join dept on dept.depton=emp.depton;
+-------------+----------+
| ename | deptname |
+-------------+----------+
| wanghongli | spider |
| masongzhao | java |
| wubinjie | java |
| jiajinsong | java |
| lihuailiang | java |
+-------------+----------+
8，子查寻(in,not in,=,!=,exists,not exists);
select * from emp where depton in (select depton from dept);
9，select 1+4;
10 ，常用函数：
mysql> select VERSION();
+-------------------------+
| VERSION() |
+-------------------------+
| 5.5.29-0ubuntu0.12.04.2 |
+-------------------------+
1 row in set (0.00 sec)
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| test1 |
+------------+
1 row in set (0.00 sec)
mysql> SELECT USER();
+----------------+
| USER() |
+----------------+
| root @localhost |
+----------------+
1 row in set (0.00 sec)
11，查看数据库支持的存储引擎：show engines \G;
mysql> show variables like 'have%';
12,索引的设计和使用。
1，myisam和innoDB都支持BTREE索引。默认情况下memory存储引擎支持HASH索引，也支持BTREE索引。mysql支持前缀索引，FULLTEXT索引（全文索引，但是只限于CHAR,VARCHAR,TEXT类型）
2，索引字段必须是非空的。
3，create index[UNIQUE|FULLTEXT|SPATIAL] cityname on city (city(10));
ALTER 添加索引。
来源：oschina
链接：https://my.oschina.net/u/1047106/blog/135140