MySQL add / delete / modify query SQL statement exercise yyds dry goods inventory

Some operations on the database ：

Get into mysql Command line : mysql -uroot –p

View all databases : show databases;

Create database ： create database wg charset utf8;

Delete database ： drop database wg;

Select database ： use databases;

View all tables ： show tables;

Look at the statement to create the database ：show create database databasename;

Look at the statement that created the table ：show create table tablename;

View table structure ：desc tablename;

increase ：

mysql> use wg;

mysql> create table students( id int auto_increment primary key,name varchar(10) not null,sex varchar(12),address varchar(50),phone int not null unique);

Log in and copy

      
      

       
       # Self growth  auto_increment
       
       

       
       # Non empty  not null
       
       

       
       # The default value is  default ‘xx’
       
       

       
       # only  unique
       
       

       
       # Specify character set  charset
       
       

       
       # Primary key  primary key
      
      
      
      

       
       
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mysql> create table scores(id int auto_increment primary key,s_id int not null,grade float not null);

data ：

mysql> insert into students (id,name,sex,phone) values(122,’wg’,’ male ’,’110’);

mysql> insert into students values(111,’wg’,’121’,’dd’) ;

Delete ：

mysql> drop table tablename;

mysql> truncate tablename; Quickly delete table data , Self growth id From the beginning , Fast , Delete directly from disk , Irrecoverable

mysql> delete from student; Delete the data of the whole table , Self growth continues

Truncate Table name

Change ：

mysql> alter table oldtable( Original table name ) rename newtable( Later table names ); Change the name of the watch

Modify table data

mysql> alter table scores( Name of table ) modify s_id( The data table ) varchar(20)( The type of watch );

mysql> alter table scores( Name of table ) change s_id（ The original name of the data ） scoresss （ The name of the data modification ）varchar(16)（ Type of data ）; Modify table structure

mysql> alter table scores（ Name of table ） add age（ Added name ） float（ Added type ）after id（ Behind whom ）; Location of new fields （age On the ID Back ）

mysql> update student set age=18; No condition specified , Modify all

mysql> update student set age=18 where name=‘hh’; Just modify it

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check ：

mysql> show create table tablename; View the new table statement

mysql> desc tablename; View table structure

mysql> show tables; View all tables

mysql> select * from students limit 5; Inquire about 5 strip

mysql> select * from students limit 1,5; Start with the number , Below n strip

mysql> SELECT * from students where sex=‘ male ’; # Specified conditions

mysql> SELECT * from students where sex=‘ male ’ and age>10; # Multiple conditions , Must satisfy at the same time

mysql> SELECT * from students where sex=‘ male ’ or sex=‘ Unknown ’ ; # Multiple conditions , One satisfaction is enough

mysql> SELECT * from students where sex !=‘ male ’; #<> It doesn't mean

mysql> SELECT * FROM students where addr like ‘% Tokyo %’;# Fuzzy matching ,% Represents a wildcard , Must use like

mysql> SELECT * from students a where a.stu_name like ‘ a surname _’;#_ Wildcards denote any single character , The word Yao can only be followed by one word

mysql> SELECT a.stu_name ‘ Student name ’,a.phone ‘ Student phone ’ from students as a where a.stu_name=‘ Yao yuan ’;# Alias a table ,as It can be omitted

SELECT * from students a where a.money BETWEEN 1000 and 10000;# Data between what

SELECT * from students ORDER BY money desc; #order by xxx desc, According to which field to continue sorting , The default is ascending , The descending order is desc, Ascending asc

SELECT * from students a where a.addr = ‘’ or a.addr is null; # Query data with empty field

SELECT DISTINCT a.money from students a ;# duplicate removal

SELECT COUNT(*) ‘ Number of students ’ from students where sex=‘ Woman ’; # The statistical number of rows

SELECT MAX(a.money) Most money from students a; # Maximum

SELECT min(money) Least money from students;# minimum value

SELECT AVG(a.money) How much is it on average from students a; # The average

SELECT sum(a.money) What's the total cost? from students a;# The sum of the

Backup database ：

mysqldump -uroot -p123456 db > db.sql

mysqldump -uroot -p123456 -A > all.sql

Restore data ：

mysql -uroot -p123456 db < db.sql

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