Day-27 database

First knowledge of database ： Additions and deletions Example

Create a xiaoming user , Let Xiao Ming have the maximum authority ( and root equally )CREATE USER ‘username’@‘host’ IDENTIFIED BY ‘password’;

 create user 'xiaoming'@'localhost'IDENTIFIED by '123';

Delete xiaoming user drop user user name @’%’;

drop user [email protected]'localhost';

# establish test database create database Database name
create database test;
# Delete test database
drop database test;
# establish Student list (student)
# Table has

id int

name varchar(30)

create table student(
id int,
name VARCHAR(30)
)
# Delete student surface
drop table student;

# Create a test_01 database , And create test_01 surface

Table has id , name , phone Please make rational use of data types

Add data to the table insert into Table name ( Name 1, Name 2) values ( value 1, value 2);

1 Zhang San 13113113111

#    2  Li Si  13213213222
 #   3  Wang Wu  13313313333

hold id by 2 Of Phone changed to 13413413444

Delete id by 3 The record of

Query all remaining records

Delete test_01 Tables and databases

create database test_01;
create table test_0111123(
   id int,
	 name VARCHAR(255),
	 phone CHAR(11)
)
INSERT	into test_0111123 (id,name,phone) VALUES(1,' Zhang San ','13113113111');
INSERT	into test_0111123 (id,name,phone) VALUES(2,' Li Si ','13113113222');
INSERT	into test_0111123 (id,name,phone) VALUES(3,' Wang Wu ','13113113333');
#update   Table name  set  Name 1= value  ,  Name 2= value   where  Name  =  value ;
update test_0111123 set phone='13413413444' where id=2;
#delete from  Table name  where  Name  =  value ;
delete from test_0111123 where id=3;
select * from test_0111123;
DROP table test_01;
DROP DATABASE test_01;

# Sign in test01 user , stay test_01 Create... Under database t_student surface , Table has id,name,sex,course,score
# among id yes int

name yes varchar

 # sex yes char
 # course yes varchar
 # score yes decimal

towards t_student Insert in table 3 Data

1 Zhang San male javaSE 99

 # 2 Li Si Woman javaWEB 98

3 Wang Wu male javEE 99.5

# stay test_01 Create... Under database t_student surface , Table has  id,name,sex,course,score
use test_01;

create table t_student(
id int,
name VARCHAR(255),
sex VARCHAR(255),
course VARCHAR(255),
score DECIMAL(5,2)
)
drop table t_student;

# insert data 
#insert into  Table name  ( Name 1, Name 2) values ( value 1, value 2);
insert into t_student(id,name,sex,course,score) VALUES(1,' Zhang San ',' male ','javaSE',99);
insert into t_student(id,name,sex,course,score) VALUES(2,' Li Si ',' Woman ','javaWEB',98);
insert into t_student(id,name,sex,course,score) VALUES(3,' Wang Wu ',' male ','javaEE',99.5);


# hold  course by javaEE The scores of   Change to 100  grammar ：update   Table name  set  Name 1= value  ,  Name 2= value   where  Name  =  value ;
   update t_student set score=100 where course='javaEE';

# hold Zhang San's gender is changed to Woman
update t_student set sex=‘ Woman ’ where name=‘ Zhang San ’;
# hold Wang Wu delete grammar ： delete from Table name where Name = value ;
delete from t_student where name=‘ Wang Wu ’;

# hold t_student Table delete
drop table t_student;
# hold test_01 Database delete
drop database test_01;
# hold test01 User deletion ( Sign in root user ) drop user user name @’%’;
drop user [email protected]‘localhost’;
FLUSH PRIVILEGES;