A database:
Create a database create databases database name ;
Delete the database drop databases database name ;
Display Database show databases;
Operation of the two database tables
1 syntax to create tables create table table name
{
Field name 1 , Data Type [ constraints ]
Field Name 2 , data type [ constraints ]
Field name 3 , the data type [ constraints ]
Field name 4 , a data type [ constraints ]
Field name 5 , data type [ constraints ]
....................................................
Field name n, the data type [ constraints ]
}
supplement:
① MySQL data types
Five basic types
An integer type: the BIT , BOOL , TINY the INT , the SMALL the INT , MEDIUM, the INT , the INT , the BIG the INT;
2 Float Type: FLOAT , DOUBLE , DECIMAL ;
3 String Type: CHAR , VARCHAR , TINY the TEXT , the TEXT , MEDIUM, the TEXT , LONGTEXT , TINY the BLOB , the BLOB , MEDIUM, the BLOB , a LONG the BLOB ;
4 date type: a Date , DateTime , TimeStamp , Time , Year ;
5 other data types: BINARY , VARBINARY , the ENUM , the SET , the Geometry , Point , MultiPoint , the LineString , a MultiLineString , Polygon , the GeometryCollection and the like .
② create a common statement
the Create the Table tb_dept ( Id int Primary Key AUTO_INCREMENT, # department number plastic primary key growth since the Name VARCHAR ( 18), # department name the Description VARCHAR ( 100) # Description 12); the Create the Table tb_emp ( the above mentioned id int Primary Key AUTO_INCREMENT, # AUTO_INCREMENT just MySQL specific the Name VARCHAR ( 18 is ), Sex VARCHAR ( 2 ), Age int, address VARCHAR ( 200 is ), in Email VARCHAR ( 100 ) );
Common operating the three-Database
# Delete table
drop table tb_dept;
# View information table
desc tb_dept;
# Note: It is not possible under any circumstances to modify, # only can be modified only when the field contains only null values.
alter table tb_emp modify sex varchar(4);
# Increase Column
Alter table tb_emp add tel varchar(4);
# Remove Columns
Alter table tb_emp drop tel varchar(4);
Alter table tb_emp drop column tel;
# Column renamed
Alter table tb_emp change Name emp_Name varchar(18);
# Table renamed
Alter table tb_emp rename emp;
Rename table emp to tb_emp;
# Restraint
/*
Not null non-empty;
Unique unique key
Primary key primary key
Check inspection
*/
# Example
Create Table tb_emp ( ID int Primary Key AUTO_INCREMENT, the Name VARCHAR ( 18 is ), Sex VARCHAR ( 2) default ' M ' check (Sex = ' M ' or Sex = ' F ' ), # table level written check in mysql ineffective Age int, address VARCHAR ( 200 is ), In Email VARCHAR ( 100 ) UNIQUE, the dept_id int, # References tb_dept (ID) # foreign key has no writing table level constraint foreign key fk_emp (the dept_id) References tb_dept (ID) ) ;