MySQL基础知识

# 启动和停用数据库

net start mysql

net stop mysql
# 登陆和退出

mysql -hlocalhost -uroot -p123;

quit;

# 注释

#

/* */

脚本中可以使用 --

# 查看版本

select version();

# 查看日期

select current_date();

# 查看当前时间

select now();

# 查看用户

select user();

# 取消未完成的输入

\c

#显示有哪些数据库

show databases;

#显示当前数据库

select database();

#创建数据库。如：创建menagerie

create database menagerie;

#切换到menagerie

use menagerie;

#通过登陆直接进入menagerie数据库

mysql -hlocalhost -uroot -p menagerie

***

#删除数据库

drop database menagerie

#显示当前数据库中的table

show tables;

#新建一个table

create table pet(name varchar(20),

owner varchar(20),

species varchar(20),

sex char(1),

birth date,

death date);

#describe显示table的结构

describe pet;

#显示表是如何创建的

show create table pet;

#删除table

drop table pet;

#insert 插入记录

insert into pet values

('Puffball','Diane','hamster','f','1999-03-30',NULL);

#select 语句

select * from pet;

#delete 删除记录

delete from pet where name=’Puffball’;

#update 将Bowse的birth 改成1989-08-31

update pet set birth='1989-08-31' where name='Bowser';

#清空table

delet from pet;

#3.5批处理

mysql -hlocalhost -uroot -p123<"d:/site/s.txt"

#或

mysql -hlocalhost -uroot -p <"d:/site/s.txt"

Enter password: ***

#或

\. d:/site/s.txt

\. d:\\site\\s.txt

#where 语句

select * from pet where name='Bowser';

#找出1998年1月1日以后出生的PET

select * from pet where birth > '1998-1-1';

#找出母狗

select * from pet where species = 'dog' and sex='f';

#找出蛇以及鸟

select * from pet where species = 'bird' or species='snake';

#找出公猫以及母狗

select * from pet where (species="cat" and sex="m") or (species="dog" and sex="f");

#显示pet的Name 和 birth

select name, birth from pet;

# UNION

select * from pet where binary pet.name regexp '^b'

union

select * from pet where binary pet.name regexp 'py$';

#找出宠物主人

select owner from pet;

#DISTINCT 只出现一次

select distinct owner from pet;

#选出猫狗的name,species,birth

select name, species, birth from pet where

species='dog' or species ='cat';

#选出name,birth 按 birth 排序

select name, birth from pet order by birth;

#选出name,birth 按 birth 倒序排序

select name, birth from pet

order by birth desc;

#强制区分大小写功能

select name, birth from pet

order by binary name desc;

#多项排序

select * from pet order by species,birth desc;

#计算日期

select name, birth, curdate(),

(year(curdate())-year(birth))

-(right(curdate(),5)<right(birth,5))

As age

from pet;

#计算年龄并按年龄排序

select name, birth, curdate(),

(year(curdate())-year(birth))-

(right(curdate(),5)<right(birth,5))

as age

from pet

order by age;

#选出已死庞物的寿命，并按寿命排序

select name,birth,death,

(year(death)-year(birth))-

(right(death,5)<right(birth,5))

as DAGE

from pet where death is not null

order by DAGE;

#选出庞物的生日

select name, birth, month(birth) from pet;

#选出下月过生日的庞物

#方法一：

select name, birth from pet

where month(birth)=

month(date_add(curdate(),interval 1 month));

#方法二，利用求余法：

select name,birth from pet

where month(birth)=

mod(month(curdate())+1,12);

#模式匹配

#_匹配单个字符，%匹配任意数目字符

#SQL默认不区分大小写

#以b开头

select * from pet where name like 'b%';

#以fy结尾

select * from pet where name like"%fy";

#找出包含w的名字

select * from pet where name like "%w%";

#找出正好五个字母的名字

select * from pet where name like "_____";

#SQL支持扩展的正则表达式

#找出以b开头的名字，使用^匹配名字的开始

#加上 binary 区分大小写

select * from pet where name regexp "^b";

#找出以fy结尾的名字

select * from pet where name regexp binary "fy$";

#找出包含w的名字

select * from pet where name regexp "w";

#找出正好五个字母的名字

select * from pet where name regexp "^.{5}$";

#计算行

select count(*) from pet;

#计算出每组的行数

select owner, count(*) from pet group by owner;

#每种动物的数量

select species, count(*) from pet group by species;

#每种性别动物的数量，性别不为空

select sex, count(*) as amount from pet where sex is not null group by sex;

#按种类和性别组合动物

select species, sex, count(*) from pet group by species, sex;

#选出猫狗。种类、性别及对应的行数

select species, sex, count(*) from pet

where species='dog' or species='cat'

group by species,sex;

#种类、性别及对应的行数

select species, sex, count(*) from pet

where sex is not null

group by species, sex;

#列的最大值

#选出最大物品号

select max(birth) as article from pet;

#拥有某个最大值的行

select * from pet where birth =

(select max(birth)from pet);

#排序后的第一行

select * from pet

order by birth desc

limit 0,1;

#按组取出列的最大值 （非一一对应）

select name, max(birth) as bd

from pet

group by species;

#拥有某个字段的组间最大值的行

#上例一一对应

select * from pet p1

where p1.birth=

(select max(p2.birth)

from pet p2

where p2.species=p1.species);

#使用auto_increment

#

create table animals(

id mediumint not null auto_increment,

name char(30) not null,

primary key(id)

);

#

insert into animals (name) values

('dog'),

('cat'),

('penguin'),

('lax'),

('whale'),

('ostrich');

#

create table animals(

grp enum('fish','mammal','bird') not null,

id mediumint not null auto_increment,

name char(30) not null,

primary key(id,grp)

);

#auto_increment 的初值设为100

alter table animals auto_increment = 100;