1.常见数据库

大型oracle,db2

中型mysql,sqlserver...

小型sqlite

2.mysql安装和卸载

停服务mysql

删除对应的文件夹

删除注册表(mysql)

3.mysql使用

1：黑窗口

2：使用工具 navicat

4.sql语句分类

数据定义语言DDL create，drop，alter，truncate

数据查询语言DQL select

数据操纵语言DML insert，delete，update

数据控制功能DCL grant 授权 ,revoke回收

5.字段

主键：primary key

自增：auto_increment

空：null

默认：default

唯一：unique

外键：foreign

......

6.类型

int

float

double

char 固定长度

varchar 长度变

text

date

time

datetime

........

7.创建数据库的命令 ‘增删改查’

-----创建数据库

create DATABASE 20201910b

---使用数据库

use 20201910b

-----创建表

create table student(

id int PRIMARY key auto_increment,

sname VARCHAR(20),

ssex VARCHAR(2),

sage int,

sscore FLOAT(4,2)

)

------修改编码

alter database 20201910b CHARSET=utf8

--------新增数据

----单条添加

INSERT into student(id,sname,ssex,sage,sscore) VALUES(1,"于磊","男",24,80.5)

-----多条添加

INSERT into student VALUES(2,"于磊1","男",25,90.5),(3,"于磊2","女",22,80),(4,"于磊3","女",19,88)

------修改数据

update 表名 set 字段=修改的数据(name =zhangsan) where 字段=值(id=1)

UPDATE student set sname='于三十' where id =2

------查询(全查，条件查询，模糊查询(_)，排序，分组)

select * from +表名

select * from student

-------条件查询

select * from student where id=1 or id =2

select * from student where id in(1,2,3,4)

select * from student where id BETWEEN 1 and 4

------模糊查询

SELECT * from student where sname like '磊%'

SELECT * from student where sname like '%磊'

SELECT * from student where sname like '%磊%'

------升序

select * from student ORDER BY sscore

----降序

select * from student ORDER BY sscore desc

------分组查询 HAVING + GROUP BY

select count(*) from student GROUP BY ssex HAVING sum(sscore)>=85

-----删除------

------物理删除+逻辑删除-------

DELETE from +表名 +where 字段=值

delete from student where id=2

------聚合函数 sum ,avg,max ,min count(),

select count(sscore) from student

select avg(sscore) from student

select max(sscore) from student

select min(sscore) from student

select sum(sscore) from student

多表联查

内连接 inner join

外连接 left join ,right join

全连接 full join (不适用mysql,使用oracle) = left join+ union+right join

取别名 as 或者是不写

--------sql语句

select s.字段,c.字段，，， from student(表1) as s inner join(left join ,right join) class(表2) c on s.字段 = c.字段

------内连接

select s.sname,s.sex,c.classroom from class c INNER JOIN student s on s.sid = c.sid

SELECT sc.school,c.classroom from school as sc INNER JOIN class as c on sc.cid = c.cid

---------外连接

select s.sname,s.sex,c.classroom from class c left JOIN student s on s.sid = c.sid (左边为主表，右边有则填充，没有用null)

select s.sname,s.sex,c.classroom from class c RIGHT JOIN student s on s.sid = c.sid (右边为主表，左边有则填充，没有用null)

----------全连接(不适用mysql)

select s.sname,s.sex,c.classroom from class c full JOIN student s on s.sid = c.sid

-------全连接

select s.sname,s.sex,c.classroom from class c left JOIN student s on s.sid = c.sid UNION select s.sname,s.sex,c.classroom from class c RIGHT JOIN student s on s.sid = c.sid

------多表联查

select c.classroom,st.sname,st.sex ,sc.school from class as c INNER join student as st on c.sid = st.sid INNER JOIN school as sc on c.cid = sc.cid

-----子查询(一个表的查询的结果作为另一个表的条件)

SELECT cid from school where school ='北京'

SELECT classroom from class where cid=(SELECT cid from school where school ='北京')

8.手机虚拟机cmd的操作命令

查询连接的设备

adb devices

开启adb服务

adb start-server

关闭adb服务

adb kill-server

安装apk

adb install 路径

卸载

adb uninstall [packagename]

查询包名

系统应用:adb shell pm list packages -s

第三方应用:adb shell pm list packages -3

查询当前应用程序的包名和启动项

adb shell dumpsys window w |findstr / |findstr name=

将移动端文件传输到电脑

adb pull 移动端路径 电脑路径

将移电脑文件传输到移动端

adb push 电脑路径 移动端路径

查看adb命令帮助信息

adb help

截屏

adb shell screencap -p 路径

log的打印

adb logcat *:E >C:\log\e.txt

Android 的日志分为如下几个级别：

V —— Verbose(最低，输出得最多)

D —— Debug

I —— Info

W —— Warning

E —— Error

F —— Fatal

S —— Silent(最高，啥也不输出)