接昨天----->>>
9. DCL
grant
revoke
10. DML语句
10.1 作用：
针对表的数据行增删改查。
10.2 种类
insert
update
delete
select
-- 10.3 insert 应用
USE test;
DESC student;
# 标准数据插入方式
INSERT student(id,NAME,age,gender,intime)
VALUES(1,'zhangs',18,'M','2020-07-02 08:30:00');
SELECT * FROM student;
INSERT INTO
student(id,NAME,age,gender,intime)
VALUES
(2,'zhang1',18,'M','2020-07-01 08:30:00'),
(3,'zhang2',19,'F','2020-07-03 08:30:00'),
(4,'zhang3',17,'M','2020-07-05 08:30:00'),
(5,'zhang4',16,'F','2020-07-06 08:30:00'),
(6,'zhang5',15,'M','2020-07-07 08:30:00');
# 省略写法
INSERT INTO
student
VALUES
(7,'zhang6',19,'M','2020-06-07 08:30:00');
# 部分列录入
INSERT INTO
student(NAME,intime)
VALUES('ma6',NOW());
SELECT * FROM student;
-- 10.4 update 应用
UPDATE student SET NAME='马六' WHERE id=8;
-- 10.5 delete 应用
DELETE FROM student WHERE id=8 ;
-- 彩蛋1： 伪删除的实现,使用update替代delete。
# 1. 添加一个状态列 state
ALTER TABLE student ADD state TINYINT NOT NULL DEFAULT 1 ;
# 2. update 替代 delete
UPDATE student SET state=0 WHERE id=9;
# 3. 查询语句修改为
SELECT * FROM student WHERE state=1;
--彩蛋2： 以下三条语句的功能及区别？
drop table t1 ; ---> 表定义+表数据（物理），全删除，磁盘空间立即删除
truncate table t1 ; ---> 清空表数据（物理），立即释放磁盘空间。
delete from t1; ---> 逐行删除表数据（逻辑，delete mark）。不会立即释放磁盘空间，会有碎片。
11. DQL 语句
11.1 select
11.1.1 作用：
获取用户表中的数据行。
-- 11.1.2 select 独立使用
# 查询系统变量（参数）
SELECT @@port;
SELECT @@basedir;
SELECT @@datadir;
SELECT @@server_id;
SELECT @@innodb_flush_log_at_trx_commit;
#替代方案：
SHOW VARIABLES;
SHOW VARIABLES LIKE '%trx%';
# 查询用户变量
SET @oldguo=100;
SELECT @oldguo;
# 查询函数
SELECT VERSION();
SELECT USER();
SELECT NOW();
SELECT CONCAT("hello world")
SELECT CONCAT(USER ,"@",HOST) FROM mysql.user;
-- 11.1.3 select 通用使用方法
# 单表查询的语法结构
/*
select 列
from 表
where 条件
group by 条件
having 条件
order by 列
limit 条件;
*/
# 导入world练习库
-- https://dev.mysql.com/doc/index-other.html
-- [root@db01 ~]# mysql -uroot -p123 < world.sql
# 了解业务
-- 1. 查看列的信息
USE world;
DESC city;
SHOW CREATE TABLE city;
/*
id : 主键列，自增长1-N。
name : 城市名字
countrycode: 城市所在国家编码(3字母，CHN、USA)
District ：城市所在区域（省、州、县）
Population ：城市人口
*/
-- 2. 查询表中部分数据
SELECT * FROM city LIMIT 10;
-- 3. 找开发沟通获取信息
# select + from 应用
-- 1. 查询全表数据(不代表生产操作) ---> cat /etc/passwd
SELECT * FROM city;
-- 2. 查询部分列数据 ---> awk $2 $5
SELECT NAME,population FROM city;
# select + from + where 应用
-- 1. where 配合等值查询
-- 例子： 查询中国(CHN)所有的城市信息
SELECT * FROM city
WHERE countrycode='CHN';
-- 例子： 查询美国(USA)所有的城市名和人口数
SELECT NAME,population FROM city
WHERE countrycode='USA';
-- 2. where 配合不等值查询 （> < >= <= !=）
-- 例子： 查询世界上人口数据小于100人的城市信息
SELECT * FROM city
WHERE population<100;
-- 3. where 配合 and or ,between and ,in 使用
-- 例子：查询中国，并且人口大于500w的城市信息
SELECT * FROM city
WHERE countrycode='CHN' AND population>5000000;
-- 例子： 查询中国或美国的城市信息
SELECT * FROM city
WHERE countrycode='CHN' OR countrycode='USA';
--- 等价写法
SELECT * FROM city
WHERE countrycode IN ('CHN','USA');
-- 例子： 查询人口数量在 100w-110w之间
SELECT * FROM city
WHERE population >=1000000 AND population<=1100000;
--- 等价写法
SELECT * FROM city
WHERE population BETWEEN 1000000 AND 1100000;
-- 4. where 配合 like应用
-- 查询countrycode是 “CH” 开头的城市信息
SELECT * FROM city
WHERE countrycode LIKE 'CH%';
# select + from + where + group by + 聚合函数 应用
-- 1. 需求 ：1000人在一个广场上，要求快速统计每个省的学生数量？
-- 1. 站队。分组
-- 2. 数数
-- 2. group by + 聚合函数的执行逻辑？
-- 1. 按照group by的列进行排序+去重复
-- 2. 讲其他的查询列进行聚合操作
-- 3. 1+2 显示给用户
-- 聚合函数种类：
/*
count() : 统计个数
sum() : 求和
avg() ：平均值
max() ：最大值
min() ：最小值
group_concat()：列转行：
*/
-- 例子1 ： 统计city表，每个国家的城市个数
SELECT countrycode,COUNT(*)
FROM city
GROUP BY countrycode;
-- 例子2 ： 统计city表，中国 每个省的 城市个数
SELECT district,COUNT(*)
FROM city
WHERE countrycode='CHN'
GROUP BY district;
-- 例子3 ： 统计city表，每个国家的总人口数
SELECT countrycode,SUM(population)
FROM city
GROUP BY countrycode;
-- 例子4 ： 统计city表，中国 每个省的总人口数
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district;
-- 例子5 ： 统计city表，中国 每个省的 城市个数 ，所有城市名
SELECT district,COUNT(*) ,GROUP_CONCAT(NAME)
FROM city
WHERE countrycode='CHN'
GROUP BY district;
# select + from + where + group by + 聚合函数 + having 应用
-- 例子： 统计city表，中国 每个省的总人口数，显示总人口数超过500w的信息
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district
having SUM(population)>5000000;
# select + from + where + group by + 聚合函数 + having +order by
-- 例子： 统计city表，中国 每个省的总人口数，显示总人口数超过500w的信息,并按照总人口排序输出。
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district
HAVING SUM(population)>5000000
order by SUM(population);
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district
HAVING SUM(population)>5000000
ORDER BY SUM(population) desc ;
# select + from + where + group by + 聚合函数 + having +order by + limit
-- 例子： 统计city表，中国 每个省的总人口数，显示总人口数超过500w的信息,并按照总人口从大倒小排序输出
-- 只显示前5名。
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district
HAVING SUM(population)>5000000
ORDER BY SUM(population) desc
limit 5 offset 0 ;
-- 只显示6-10名。
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district
HAVING SUM(population)>5000000
ORDER BY SUM(population) DESC
LIMIT 5,5;
SELECT district,SUM(population)
FROM city
WHERE countrycode='CHN'
GROUP BY district
HAVING SUM(population)>5000000
ORDER BY SUM(population) DESC
LIMIT 5 offset 5;
====================================================================
# 多表连接查询
-- 1. 预备工作
CREATE DATABASE school CHARSET utf8;
USE school
CREATE TABLE student(
sno INT NOT NULL PRIMARY KEY AUTO_INCREMENT COMMENT '学号',
sname VARCHAR(20) NOT NULL COMMENT '姓名',
sage TINYINT UNSIGNED NOT NULL COMMENT '年龄',
ssex ENUM('f','m') NOT NULL DEFAULT 'm' COMMENT '性别'
)ENGINE=INNODB CHARSET=utf8;
CREATE TABLE course(
cno INT NOT NULL PRIMARY KEY COMMENT '课程编号',
cname VARCHAR(20) NOT NULL COMMENT '课程名字',
tno INT NOT NULL COMMENT '教师编号'
)ENGINE=INNODB CHARSET utf8;
CREATE TABLE sc (
sno INT NOT NULL COMMENT '学号',
cno INT NOT NULL COMMENT '课程编号',
score INT NOT NULL DEFAULT 0 COMMENT '成绩'
)ENGINE=INNODB CHARSET=utf8;
CREATE TABLE teacher(
tno INT NOT NULL PRIMARY KEY COMMENT '教师编号',
tname VARCHAR(20) NOT NULL COMMENT '教师名字'
)ENGINE=INNODB CHARSET utf8;
INSERT INTO student(sno,sname,sage,ssex)
VALUES
(1,'zhang3',18,'m'),
(2,'zhang4',18,'m'),
(3,'li4',18,'m'),
(4,'wang5',19,'f'),
(5,'zh4',18,'m'),
(6,'zhao4',18,'m'),
(7,'ma6',19,'f'),
(8,'oldboy',20,'m'),
(9,'oldgirl',20,'f'),
(10,'oldp',25,'m');
INSERT INTO teacher(tno,tname) VALUES
(101,'oldboy'),
(102,'hesw'),
(103,'oldguo')
(104,'alex');
INSERT INTO course(cno,cname,tno)
VALUES
(1001,'linux',101),
(1002,'python',102),
(1003,'mysql',103)
(1004,'go',105);
INSERT INTO sc(sno,cno,score)
VALUES
(1,1001,80),
(1,1002,59),
(2,1002,90),
(2,1003,100),
(3,1001,99),
(3,1003,40),
(4,1001,79),
(4,1002,61),
(4,1003,99),
(5,1003,40),
(6,1001,89),
(6,1003,77),
(7,1001,67),
(7,1003,82),
(8,1001,70),
(9,1003,80),
(10,1003,96);
-- 2. 多表连接的类型
-- 笛卡尔乘积
mysql> select * from teacher , course;
+-----+--------+------+--------+-----+
| tno | tname | cno | cname | tno |
+-----+--------+------+--------+-----+
| 101 | oldboy | 1001 | linux | 101 |
| 102 | hesw | 1001 | linux | 101 |
| 103 | oldguo | 1001 | linux | 101 |
| 104 | alex | 1001 | linux | 101 |
| 101 | oldboy | 1002 | python | 102 |
| 102 | hesw | 1002 | python | 102 |
| 103 | oldguo | 1002 | python | 102 |
| 104 | alex | 1002 | python | 102 |
| 101 | oldboy | 1003 | mysql | 103 |
| 102 | hesw | 1003 | mysql | 103 |
| 103 | oldguo | 1003 | mysql | 103 |
| 104 | alex | 1003 | mysql | 103 |
| 101 | oldboy | 1004 | go | 105 |
| 102 | hesw | 1004 | go | 105 |
| 103 | oldguo | 1004 | go | 105 |
| 104 | alex | 1004 | go | 105 |
+-----+--------+------+--------+-----+
-- 内连接 （取交集）
SQL92:
mysql> select *from teacher , course where teacher.tno=course.tno;
SQL99:
mysql> select *from teacher join course on teacher.tno=course.tno;
+-----+--------+------+--------+-----+
| tno | tname | cno | cname | tno |
+-----+--------+------+--------+-----+
| 101 | oldboy | 1001 | linux | 101 |
| 102 | hesw | 1002 | python | 102 |
| 103 | oldguo | 1003 | mysql | 103 |
+-----+--------+------+--------+-----+
-- 外连接 （左、右）
mysql>
mysql> select * from teacher left join course on teacher.tno = course.tno;
+-----+--------+------+--------+------+
| tno | tname | cno | cname | tno |
+-----+--------+------+--------+------+
| 101 | oldboy | 1001 | linux | 101 |
| 102 | hesw | 1002 | python | 102 |
| 103 | oldguo | 1003 | mysql | 103 |
| 104 | alex | NULL | NULL | NULL |
+-----+--------+------+--------+------+
4 rows in set (0.00 sec)
mysql> select * from teacher right join course on teacher.tno = course.tno;
+------+--------+------+--------+-----+
| tno | tname | cno | cname | tno |
+------+--------+------+--------+-----+
| 101 | oldboy | 1001 | linux | 101 |
| 102 | hesw | 1002 | python | 102 |
| 103 | oldguo | 1003 | mysql | 103 |
| NULL | NULL | 1004 | go | 105 |
+------+--------+------+--------+-----+
-- 3. 多表连接语法格式
select xxx
from a join b
on a.x=b.y
where
group by
having
order by
limit
select xxx
from a join b
on a.x=b.y
join c
on b.z=c.zz
核心思路：
1.找到所有相关表
2.找到所有表之间的关联关系
3.罗列其他的查询条件
--3. 多表连接例子：
--- 统计学员zhang3,学习了几门课
SELECT student.sname,COUNT(*)
FROM student JOIN sc
ON student.sno =sc.sno
WHERE student.sname='zhang3';
--- 所有学员学习的课程门数
SELECT student.sname,COUNT(*)
FROM student JOIN sc
ON student.sno =sc.sno
GROUP BY student.sname;
--- 查询zhang3,学习的课程名称有哪些?
SELECT student.sname,GROUP_CONCAT(course.cname)
FROM student
JOIN sc
ON student.sno=sc.sno
JOIN course
ON sc.cno=course.cno
WHERE student.sname = 'zhang3'
GROUP BY student.sname;
-- 课堂练习：
--- 查询oldguo所教课程的平均分数
SELECT teacher.tname ,AVG(sc.score) FROM
teacher
JOIN course
ON teacher.tno=course.tno
JOIN sc
ON course.cno=sc.cno
WHERE teacher.tname='oldguo'
GROUP BY teacher.tname;
--- 每位老师所教课程的平均分,并按平均分排序
SELECT teacher.tname ,AVG(sc.score) FROM
teacher
JOIN course
ON teacher.tno=course.tno
JOIN sc
ON course.cno=sc.cno
GROUP BY teacher.tname
ORDER BY AVG(sc.score);
--- 查询oldguo所教的不及格的学生姓名
SELECT teacher.tname,GROUP_CONCAT(student.sname) FROM
teacher
JOIN course
ON teacher.tno=course.tno
JOIN sc
ON course.cno=sc.cno
JOIN student
ON sc.sno=student.sno
WHERE teacher.tname='oldguo' AND sc.score<60
GROUP BY teacher.tname ;
--- 查询所有老师所教学生不及格的信息
SELECT teacher.tname,GROUP_CONCAT(student.sname) FROM
teacher
JOIN course
ON teacher.tno=course.tno
JOIN sc
ON course.cno=sc.cno
JOIN student
ON sc.sno=student.sno
WHERE sc.score<60
GROUP BY teacher.tname ;
# 别名的使用
-- 表别名
SELECT a.tname,GROUP_CONCAT(d.sname) FROM
teacher AS a
JOIN course AS b
ON a.tno=b.tno
JOIN sc AS c
ON b.cno=c.cno
JOIN student AS d
ON c.sno=d.sno
WHERE c.score<60
GROUP BY a.tname ;
-- 列别名
SELECT a.tname AS aa ,GROUP_CONCAT(d.sname) AS bb FROM
teacher AS a
JOIN course AS b
ON a.tno=b.tno
JOIN sc AS c
ON b.cno=c.cno
JOIN student AS d
ON c.sno=d.sno
WHERE c.score<60
GROUP BY a.tname ;
SELECT teacher.tname AS '老师名' ,AVG(sc.score) AS '平均分' FROM
teacher
JOIN course
ON teacher.tno=course.tno
JOIN sc
ON course.cno=sc.cno
GROUP BY teacher.tname
ORDER BY 平均分;
11.2 元数据的获取
11.2.1 元数据包含什么？
数据字典信息（表属性、列、列属性）、状态、系统参数、权限等。
ibdata1 、 frm 、 mysql库（权限表、状态表、统计信息） 、 P_S、SYS表
11.2.2 查询换数据方法
# show 语句
help show
show databases;
show tables [from DB];
show create database world;
show craete table world.city;
show full processlist;
show engines;
show charset;
show collation;
show variables [like '%%']
show status [like '%%']
show grants for
SHOW OPEN TABLES
SHOW INDEX FROM tbl_name
SHOW MASTER STATUS
SHOW BINLOG EVENTS
SHOW RELAYLOG EVENTS
SHOW SLAVE STATUS
SHOW SLAVE HOSTS
# information_schema 视图库
每次数据库启动，自动在内存中生成的“虚拟表”（视图）。
保存了各种常用元数据查询方法的视图，只能查询不能修改和删除。
-- TABLES 使用
-- 1. 结构介绍
作用：存储了整个MySQL中所有表相关属性信息
desc tables;
TABLE_SCHEMA : 所在库
TABLE_NAME ： 表名
ENGINE ： 存储引擎
TABLE_ROWS ： 数据行
AVG_ROW_LENGTH ： 平均行长度
INDEX_LENGTH ： 索引的长度
DATA_FREE ： 碎片的情况
-- 2. 应用案例
-- 例子1： 统计MySQL所有业务库：库名、表个数、表名
select table_schema,count(*),group_concat(table_name)
from information_schema.tables
where table_schema not in ('mysql','sys','information_schema','performance_schema')
group by table_schema ;
-- 例子2： 统计MySQL所有业务库：库名、数据总量(单张表：TABLE_ROWS*AVG_ROW_LENGTH+INDEX_LENGTH)
select table_schema,sum(TABLE_ROWS*AVG_ROW_LENGTH+INDEX_LENGTH)/1024/1024 as sum_mb
from information_schema.tables
where table_schema not in ('mysql','sys','information_schema','performance_schema')
group by table_schema ;
-- 例子3:
生产案例：客户MySQL系统 经历的很多个版本 5.1 --》 5.5 ---》 5.6。。。
系统中有2000-3000张表，其中有myisam、innodb两种存储引擎类型。
需求1： 查找业务库中，所有非InnoDB表
select table_schema,table_name,engine
from information_schema.tables
where table_schema not in ('mysql','sys','information_schema','performance_schema') and engine !='innodb';
需求2： 将所有这些表备份走
mysqldump -uroot -p123 test t1 >/data/test_t1.sql
select concat("mysqldump -uroot -p123 ",table_schema," ",table_name," >/data/",table_schema,"_",table_name,".sql")
from information_schema.tables
where table_schema not in ('mysql','sys','information_schema','performance_schema') and engine !='innodb'
into outfile '/tmp/dump.sh';
需求3: 将以上表替换为InnoDB引擎
alter table test.t1 engine=innodb;
select concat("alter table ",table_schema,".",table_name," engine=innodb;")
from information_schema.tables
where table_schema not in ('mysql','sys','information_schema','performance_schema') and engine !='innodb'
into outfile '/tmp/alter.sql';
[root@db01 ~]# sh /tmp/dump.sh
[root@db01 ~]# cd /data/
[root@db01 data]# ll
-rw-r--r-- 1 root root 1741 Jul 2 18:30 test_t1.sql
-rw-r--r-- 1 root root 1741 Jul 2 18:30 world_t2.sql
[root@db01 data]# mysql -uroot -p123
mysql> select table_schema,table_name,engine from information_schema.tables where table_schema not in ('mysql','sys','information_schema','performance_schema') and engine !='innodb';
Empty set (0.00 sec)