1.2 to create a data table

Create a data table

It belongs to a data definition language DDL

Syntax:

create table [if not exists] `表名`(
    '字段名1' 列类型 [属性][索引][注释],
    '字段名2' 列类型 [属性][索引][注释],
    #...
    '字段名n' 列类型 [属性][索引][注释]
)[表类型][表字符集][注释];

Description: Anti-quotes are used (keyboard esc key below) the difference between MySQL reserved words and common character introduced.

And column data types

Column type: a predetermined type of data stored in the database of the column

1. Numeric types

2. String type

3. The date and time type

4. NULL value

• Understood as "no value" or "unknown value"
• Do not perform arithmetic operations with NULL, the result is still NULL

Data field properties

UnSigned :

• Unsigned integer
• Declare the data column does not allow negative.

ZEROFILL :

• 0 filled
• Insufficient number of bits are padded with zeros, such as int (3), 5, compared with 005

Auto_InCrement :

• Automatic increase, adding each piece of data, an automatic (default) on a number of records
• Is typically used to set the primary key index, you must be an integer type.
• Define the start value and the step size
  • The current table setting step (AUTO_INCREMENT = 100): Table affects only the current
  • SET @@ auto_increment_increment = 5; increment affect all tables (global)

NULL and NOT NULL:

• The default is NULL, i.e., no value is inserted into the column
• If set to NOT NULL, the column must have a value

DEFAULT :

• default
• For setting default values
  • For example, the gender field, the default is "male", otherwise "female"; if no value is specified for the column, is "man" is the default value

/*创建数据表例子

1、创建一个名为School01的数据库。

1、创建一个学生信息表：学生id（自增，主键），姓名，年龄，性别，电话，籍贯，入学时间，所属班级id（外键）。

2、创建一个学生成绩表：成绩id（自增，主键），科目，成绩，学生id（外键），创建时间。

3、创建一个学生班级表：班级id（主键，自增），班级名称。

*/

#如果存在数据库School，则删除。否则创建数据库
DROP DATABASE IF EXISTS `School01`;
#创建数据库
CREATE DATABASE `School01`;
USE `School01`;
#如果存在数据表，则删除，否则创建
DROP TABLE IF EXISTS `tb_class`;
#创建一个学生班级表：班级id（主键，自增），班级名称。
CREATE TABLE `tb_class`
(
`id` INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY ,
`Name` VARCHAR(32) NOT NULL

);
DROP TABLE IF  EXISTS tb_student;
#创建一个学生信息表：学生id（自增，主键），姓名，年龄，性别，入学时间，所属班级id（外键）。
CREATE TABLE `tb_student`
(
 `id` INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
 `Name` VARCHAR(32) NOT NULL,
 `Age` INT DEFAULT 0,CHECK(`Age`>0 AND `Age`<=100),
 `gender` BOOLEAN DEFAULT 0,CHECK(`gender`=0 OR `gender`=1),
 `date` DATETIME DEFAULT NOW()
);
#创建一个学生成绩表：成绩id（自增，主键），科目，成绩，学生id（外键），创建时间。
DROP TABLE IF EXISTS `tb_score`;
CREATE TABLE `tb_score`
(`id` INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
`course` VARCHAR(32) NOT NULL,
`Score` FLOAT(3,1) NOT NULL,
`stuId` INT(11) NOT NULL , 
CONSTRAINT `FK_Stuid` FOREIGN KEY(`stuId`) REFERENCES `tb_student`(`id`)
);

Result: The

type of MySQL data tables: MyISAM , InnoDB , HEAP, BOB, CSV, etc. ...

Common MyISAM and InnoDB type

name	MyISAM	InnoDB
Transaction Processing	not support	stand by
Datarows	not support	stand by
Foreign key constraint	not support	stand by
Full-text index	stand by	not support
Table space size	Small	Large, approximately 2-fold

• Applicable MyISAM: the corresponding velocity and space-saving
• Applicable InnoDB: security, transaction processing and multi-user operating data table