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notes ：SQL The homework , The other day's library 、 surface , It's all about building the foundation ; None of this , Add, delete, modify and check later , You can't play ;

1）isTester Table fields 、 type 、 attribute ：

id INT(10) NOT NULL UNIQUE PRIMARY KEY ,

uname VARCHAR(20) NOT NULL ,

sex VARCHAR(4) ,

birth YEAR,

department VARCHAR(20) ,

address VARCHAR(50) ,

idoxu VARCHAR(20)

2）idoxu Table fields 、 type 、 attribute ：

id INT(10) NOT NULL UNIQUE PRIMARY KEY AUTO_INCREMENT ,

stu_id INT(10) NOT NULL ,

c_name VARCHAR(20) ,

istester VARCHAR(50) ,

grade INT(10)

Method 1 ： Graphical tools

Method 2 ： Command line

create table istester(

id ...);

The first 3 Day job

According to the existing table istester and idoxu Create new table （ Copy table ）

1） Copy istester Table structure , Create new table istester2

notes ： There are two ways

2） Copy idoxu Table structure and data , Create new table idoxu2

3） Copy idoxu Table structured id,stu_id,istester Three fields , Create new table idoxu3

Method 1 ：

Right click the copy table directly and rename it

Method 2 ：

1） Copy istester Table structure , Create new table istester2

notes ： There are two ways

create table istester2 like istester ;

create table idoxu2 as select * from idoxu where 2=1;

2） Copy idoxu Table structure and data , Create new table idoxu3

create table idoxu3 as select * from idoxu

3） Copy idoxu Table structured id,stu_id,istester Three fields , Create new table idoxu3

create table idoxu3 as select id,stu_id,istester from idoxu where 1<>1;

The first 4 Day job

1） Delete table istester2

2） Delete table at the same time idoxu2 and idoxu3

3） See what other tables are available

The first 5 Day job

1） modify istester surface , Add a field istester6 （ Character type VARCHAR, length 100, Not allowed to be empty ）

2） View fields istester6 , Whether to add successfully

3） modify istester surface , Delete field istester6

4） Acknowledgement field istester6 , Delete successfully

show columns from istester = desc istester

The first 6 Day job ,

Insert insert：

1） To watch istester insert data

id = 1 ,uname = idoxu ,idoxu = 2020

id = 2 ,uname = idoxu2 ,idoxu = 2020

id=11,uname = idoxu3,sex=1

id=12,uname = idoxu4,sex=2

id=13,uname = idoxu5,sex=1

id=14,uname = idoxu6,sex=2

2） To watch idoxu insert data

id=4,stu_id=11,c_name=idoxu,grade=90

id=5,stu_id=12,c_name=lin,grade=100

id=6,stu_id=33,c_name=istester,grade=20

The first 7 Day job

1） Inquire about istester surface id = 1 The content of

2） Inquire about idoxu surface grade=100 The content of

The first 8 Day job

continue select
1） lookup idoxu surface , name （c_name） contain “i” The data of

2） lookup istester surface ,id contain “1” The data of

3） lookup istester surface ,id contain “1” The data of , Press id Descending

4） lookup istester surface ,id contain “1” The data of , take id The biggest three

select * from istester where uname like '%i%';

The first 9 Day job

1） find idoxu In the table , Students with the highest scores and scores

2） find idoxu In the table , Students with the lowest scores and scores

Method 2 ： Subquery + function

The first 10 Day job

-- 1) find istester surface ,sex Empty data ;

-- 2） to update istester surface , hold sex Empty , Set to 0（ Gender unknown ）

-- 3） find idoxu surface ,grade Less than 60 Classmate

-- 4） to update idoxu surface , hold grade Less than 60 Classmate , All changed to 59 branch

The first 11 Day job

-- 1） lookup istester surface , Press id Descending

-- 2） lookup idoxu surface , Press grade Ascending

The first 12 Day job

1） Inquire about istester surface , How many pieces of data are there

2） Inquire about istester surface , There are several gender types （sex Field , duplicate removal ）

The first 13 Day job

1） lookup idoxu surface , Student achievement (grade) Total score

2） lookup idoxu surface , Student achievement (grade) average

The first 14 Day job

1） lookup idoxu surface , Achievements in 80 - 100 Students in the section ;（ continuity ）

2） lookup istester surface ,id by 2,11,12 The data of ;（ Discontinuous ）

The first 15 Day job

1） Delete istester surface ,id Greater than 12 The data of ;

2） Delete idoxu surface , fraction grade fail, （ Less than 60 branch ） The data of ;

The first 16 Day job ***

1） To build the data , hold istester All data of table , Insert into idoxu surface

Field value rules

id take id

stu_id take id

c_name take uname

istester and grade Field , Give default 60

The first 17 Day job

-- 1） Modify table idoxu, Put field istester , Change it to istester6（ Character type varchar, length 160 ）

-- 2） Check whether the modification is successful

-- 3） hold idoxu surface , Renamed as idoxu6

-- 4） Check whether the modification is successful

The first 18 Day job ***

1） Create database istesterdb6

2） Check whether the database is created successfully ;

3） Get into istesterdb6 library

4） In the database istesterdb6 , establish idoxu surface , Direct copy istester library idoxu6 Data and structure of tables ;

5） Check whether the table was created successfully ;

The first 19 Day job

idoxu surface , fraction grade

1） Top three students And fractions ;

2） ranking 3 - 6 Students of And fractions ;

3） ranking 6 All students after And fractions ;

The first 20 Day job

Multiple tables （ Left link 、 Right link 、 Inner link ）

surface idoxu6 and surface istester

The first 21 Day job

1） Keep watch idoxu6, Change it to idoxu

2） Delete Library istesterdb6

3） Delete istester surface

4） Empty idoxu The data table

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