Basic MySQL

DDL
Database operation

show databases;
create databases;
use  Database name ;
select database();
drop database  Database name ;

Table operations

show tables;
create table  Table name ( Field   Field type  , Field   Field type );
desc  Table name ;
show create table  Table name ;
alter table  Table name  add/rename to...;
alter table  Table name  modify  Field name   New data types ( length );
alter table  Table name  change  Old field name   new field name   type ( length ) [comment  notes ][ constraint ];
drop table  Table name ;

DML

insert into  Table name ( Field 1, Field 2..)values( value 1, value 2,..);
update  Table name  set  Field 1= value 1,where  Conditions ;
delete from  Table name  where  Conditions ;

DQL


DCL
User management

create user ' user name '@' Host name ' identified by ' password ';
alter user ' user name '@' Host name ' identified with mysql_native_password by ' password ';
drop user ' user name '@' Host name ';

Access control

grant  Permission list  on  Database name . Table name  to ' user name '@' Host name ';
revoke  Permission list  on  Database name . Table name  from ' user name '@' Host name ';

function

1. String function
   

2. Numerical function
   

3. Date function
   

4. Flow function
   

constraint

1. Non empty constraint ：not null
2. Unique constraint ：unique
3. Primary key constraint ：primary key( Self increasing :auto_increment)
4. Default constraint ：default
5. Check constraint ：check
6. Foreign key constraints ：foreign key

Multi-table query

1. Multi table relation
   

2. Multi-table query
   

Business
A transaction is a collection of operations , Or it all works , Or all failed .

start transaction;-- Open transaction 
commit/rollback;-- Submit / Roll back the transaction 

Four characteristics ACID

Atomicity （Atomicity): Transactions are the smallest and indivisible unit of operations , All or nothing , All or nothing .
Uniformity (Consistency) : When the transaction completes , All data must be kept consistent .
Isolation, （lsolation): The isolation mechanism provided by the database system , Ensure that transactions run in an independent environment that is not affected by external concurrent operations .
persistence (Durability): Once a transaction is committed or rolled back , Its changes to the data in the database are permanent .

Transaction isolation level