Teach you to easily learn the type of data stored in the database (a must see for getting started with the database)

Database storage data type

Catalog

data type

1 numeric Numeric type

2 string character string

3 date、time、datetime Date related type

4 enum set The compound type

5 bit Boolean

6 json

7 binary Binary system

---

1 numeric Numeric type

Integers ： tinyint smallint mediumint int bigint

decimal ：float double decimal(p,s) numeric(p,s)

 

-- Create a table ( Field columns use data types ) 
create table student( id int unsigned auto_increment, name varchar(30), 
/* age bigint ,  You can't write it like that ,bigint  It's occupation 8 byte  */
 age tinyint,
 /*  Integers can only store integers  18*/ 
money decimal(10,2),
/* 99999999.99  Maximum number   If there is no number, it is  0.00 */
primary key(id) );
-- insert data 
 insert into student values(null,'jack',18,200);
-- Query data 
 select * from student;

 

-- unsigned  demonstration 
-- age int
-- age int unsigned  Unsigned , No negative number , from 0 Start   Fast 
-- zerofill 0 fill  
-- age int(3) zerofill , If you insert a number 1  When querying 001
-- 3 On behalf of the digital 3 Bit width , No 3 digit , If not three , Then fill in the front 0 
create table t1( name varchar(30),n1 int, n2 int unsigned, n3 int(3),
 /* here 3 No meaning, no effect */ 
n4 int(5) zerofill);
/*  If the content is not enough 5 position , Then fill 0 */ 
insert into t1 values('jack',1,2,3,4);
 select * from t1;
 -- jack 1 2 3 00004
 insert into t1 values('lisi',-1,0,-3,2342342);

2 string character string

char(n) varchar(n) tinytext text mediumtext longtext

char(0-255)

varchar(0-21835)

 

 

3 date、time、datetime Date related type

date yyyy-MM-dd

time hh:mm:ss

datetime yyyy-MM-dd hh:mm:ss

timestamp Time stamp yyyy-MM-dd hh:mm:ss

 

4 enum set The compound type

enum enumeration

set aggregate

 

5 bit Boolean

bit A type of , Can only store 1 or 0 Actually mysql The bottom layer uses 　tinyint unsigned

 

6 json

json Is a special string , Lightweight data format , Data exchange formats in different languages are not required .

JSON(JavaScript Object Notation, JS Object shorthand ) Is a lightweight data exchange format . It's based on ECMAScript ( Developed by the European Computer Association js standard ) A subset of , Use text format completely independent of programming language to store and represent data . Jane Clean and clear hierarchy makes JSON Become the ideal data exchange language . Easy to read and write , It's also easy to machine analyze and Generate , And effectively improve the network transmission efficiency .

 

7 binary Binary system

binary(255)

varbinary()

blob