mysql必知必会笔记

db

dbms

table

schema

column

datatype

row/record

primary key 

// =======================command====================

show databases;

use dbname;       --->Database changed

show tables;     

show columns from tbname;

--->>shortcut------>describe tbname;

help show;

show status;

show create database dbname;

show create table tbname;

show grants;   ( view user permission)

// ---------------------------------------------search----select--------------------------------------

select * from tbname;

select columnname from tbname;

select distinct clname from tbname;

select count(distinct clname) from tbname;

select clname from tbname limit clnum,recordnum(starting from 0);

select clname from tbname limit recordnum(starting from 0) offset clnum;

select tbname.clname from dbname.tbname;

 // -------------------------------------------------datatype-------------------------------------------

D1.String datatype

char(1~255fixed-length string,the length must be specified at the time of creation.(default char(1)))

enum 

longtext

mediumtext

set

text

tinytext

varchar(variable length sttring)

D2.Numeric datatype

bit

bigint

boolean(or bool)

decimal(or dec)

double

float

int(or integer)

mediumint

real

smallint

tinyint

D3.Date and time datatype

date(1000-01-01~9999-12-31  format=YYYY-MM-DD)

datetime    date+time

timestamp

time(format=HH:MM:SS)

year(70(1970~69(2069))     1901~2155)

D3.Binary datatype

blob   (max length: 64KB)

mediumblob   (max length:16MB)

longblob(max length:4GB)

tinyblob(max length:255byte)

 

 

mysql列名包含空格等的处理方式收藏

https://www.cnblogs.com/lzxianren/p/trick-problem.html