MySQL statement

What is? sql sentence

Structured query language , Is a special purpose programming language , For storing data and querying , Update and manage relational database system , It is also the extension of database script file .

frequently-used sql sentence

DDL( Data definition language )

Create a library         create database  Library name ;         

Show all libraries         show databases;                   

Delete a library         drop database  Library name ;             

Use the library                 use Library name ;                               

Build table                     create   table    Table name （ Field name type attribute , Field name type attribute ）;

View all the tables in the library        show  tables;   

View table structure           desc Table name ;       

View table structure           show   create   table  Table name ;           

Delete table                 drop table    Table name ;     

Modify the name of the table         alter     table  The old name of the table   rename  as The new name of the table ;

Modify fields         alter    table    Table name   modify  Field name     New data types New type length   New default   New notes ; 

Add fields         alter    table    Table name    add  Field name data type   Type length   The default value is   notes ;

Modify fields           alter  table    Table name   change    Old field name   new field name   

Delete field           alter table  Table name   drop  Field name

DML( Data operation language )

Add data         insert  into  Table name （ Field name , Field name ... Field name ）values （ value , value ... value ）;

Add multiple pieces of data at one time         insert  into Table name （ Field name , Field name ）values（ value , value ）,（ value , value ）;

Modifying data         update  Table name   set  Field name = value , Field name = value ...where Clause

Delete data         delete  from  Table name   where Clause

Delete all data in the table         delete  from  Table name

Clear the table         truncate  Table name

DQL( Data control statement )

  Inquire about        select Field name ... Field name from Table name

Remove duplication         select distinct Field name from Table name

The field is aliased         select Field name as Alias   from  Table name

Conditions of the query         select  Field name   from  Table name   where  Clause

grouping         group by

Conditions of the query         having（ Query with conditions after grouping ）

Sort         order by   （desc Descending   asc Ascending ）

Pagination         limit[n,m]  n( The current page number -1)* Page capacity   m Page capacity

Fuzzy query         like   （% Any number of any characters ） （_ An arbitrary character ）

Find in a specific range     in

Non equivalent associated query         select  *  from  Table name , Table name

Equivalent joint query         select  *  from  Table name 1, Table name 2  where surface 1. Field = surface 2. Field

Inline query         select   *  from surface 1  inner  join  surface 2  on  surface 1. Field = surface 2. Field      

Outreach query （ Left query ）        select  *  from  surface 1（ Main table ）left  join  surface 2  on    surface 1. Field = surface 2. Field  

Outreach query （ Right query ）        select  *  from  surface 1  fight  join  surface 2（ Main table ）  on    surface 1. Field = surface 2. Field  

Merging and removing weights         select Field name , Field name   from  Table name 1  union  select  Field name , Field name   form  Table name 2（ When the number of columns of two tables queried is not equal , Will report a mistake ）

Merge without redoing      select Field name , Field name   from  Table name 1  union all  select  Field name , Field name   form  Table name 2