MySQL-基础语法
#启动mysql服务器
net start mysql
#关闭
net stop mysql
#进入
mysql -h 主机地址 -u 用户名 -p 用户密码
#退出
exit
status;
显示当前mysql的version的各种信息。
#-----MySql数据库操作基础-----
#显示数据库
show databases;
#判断是否存在数据库wpj1105,有的话先删除
drop database if exists xianyu007;
#创建数据库
create database xianyu007;
#删除数据库
drop database xianyu007;
#使用该数据库
use xianyu007;
#显示数据库中的表
show tables;
#先判断表是否存在,存在先删除
drop table if exists student;
#创建表
create table student(
id int auto_increment primary key,
name varchar(50),
sex varchar(20),
date varchar(50),
content varchar(100)
)default charset=utf8;
#删除表
drop table student;
#查看表的结构
describe student; #可以简写为desc student;
#插入数据
insert into student values(null,'aa','男','1988-10-2','......');
insert into student values(null,'bb','女','1889-03-6','......');
insert into student values(null,'cc','男','1889-08-8','......');
insert into student values(null,'dd','女','1889-12-8','......');
insert into student values(null,'ee','女','1889-09-6','......');
insert into student values(null,'ff','null','1889-09-6','......');
#查询表中的数据
select * from student;
select id,name from student;
#修改某一条数据
update student set sex='男' where id=4;
#删除数据
delete from student where id=5;
# and 且
select * from student where date>'1988-1-2' and date<'1988-12-1';
# or 或
select * from student where date<'1988-11-2' or date>'1988-12-1';
#between
select * from student where date between '1988-1-2' and '1988-12-1';
#in 查询制定集合内的数据
select * from student where id in (1,3,5);
#排序 asc 升序 desc 降序
select * from student order by id asc;
#分组查询 #聚合函数
select max(id),name,sex from student group by sex;
select min(date) from student;
select avg(id) as '求平均' from student;
select count(*) from student; #统计表中总数
select count(sex) from student; #统计表中性别总数 若有一条数据中sex为空的话,就不予以统计~
select count(ifnull(sex,0)) from students #统计表中性别总数 若有一条数据中sex为空也统计~
select sum(id) from student;
#查询第i条以后到第j条的数据(不包括第i条)
select * from student limit 2,5; #显示3-5条数据
#修改数据
update c set age=66 where id=2;
update c set name='花花',age=21,sex='女' where id=2
delete from c where age=21;
#常用查询语句
select name,age ,id from c
select * from c where age>40 and age<60; #and
select * from c where age<40 or age<60; #or
select * from c where age between 40 and 60 #between
select * from c where age in (30,48,68,99); #in 查询指定集合内的数据
select * from c order by age desc; #order by (asc升序 des降序)
#分组查询
select name,max(age) from c group by sex; #按性别分组查年龄最大值
#聚合函数
select min(age) from c;
select avg(age) as '平均年龄 ' from c;
select count(*) from c; #统计表中数据总数
select sum(age) from c;
#修改表的名字
#格式:alter table tbl_name rename to new_name
alter table c rename to a;
#表结构修改
create table test
(
id int not null auto_increment primary key, #设定主键
name varchar(20) not null default 'NoName', #设定默认值
department_id int not null,
position_id int not null,
unique (department_id,position_id) #设定唯一值
);
#修改表的名字
#格式:alter table tbl_name rename to new_name
alter table test rename to test_rename;
#向表中增加一个字段(列)
#格式:alter table tablename add columnname type;/alter table tablename add(columnname type);
alter table test add columnname varchar(20);
#修改表中某个字段的名字
alter table tablename change columnname newcolumnname type; #修改一个表的字段名
alter table test change name uname varchar(50);
select * from test;
#表position 增加列test
alter table position add(test char(10));
#表position 修改列test
alter table position modify test char(20) not null;
#表position 修改列test 默认值
alter table position alter test set default 'system';
#表position 去掉test 默认值
alter table position alter test drop default;
#表position 去掉列test
alter table position drop column test;
#表depart_pos 删除主键
alter table depart_pos drop primary key;
#表depart_pos 增加主键
alter table depart_pos add primary key PK_depart_pos
(department_id,position_id);
# 表students 增加外键
alter table students add foreign key(cls_id) references classes(id);
# 表students 查看外键
alter table teacher drop foreign key 外键名;
# 表students 删除外键
alter table teacher drop foreign key 外键名;
# 内连接查询语法格式:
# select 字段 from 表1 inner join 表2 on 表1.字段1 = 表2.字段2
select * from students as s inner join classes as c on s.cls_id = c.id;
# 左连接查询语法格式:
# select 字段 from 表1 left join 表2 on 表1.字段1 = 表2.字段2
select * from students as s left join classes as c on s.cls_id = c.id;
# 右连接查询语法格式:
# select 字段 from 表1 right join 表2 on 表1.字段1 = 表2.字段2
select * from students as s right join classes as c on s.cls_id = c.id;
# 自连接查询
# 自连接查询必须对表起别名
# 自连接查询就是把一张表模拟成左右两张表,然后进行连表查询。
# 自连接就是一种特殊的连接方式,连接的表还是本身这张表
select c.id, c.title, c.pid, p.title from areas as c inner join areas as p on c.pid = p.id where p.title = '山西省';
#用文本方式将数据装入数据库表中(例如D:/mysql.txt)
load data local infile "D:/mysql.txt" into table MYTABLE;
#导入.sql文件命令(例如D:/mysql.sql)
source d:/mysql.sql; #或者 /. d:/mysql.sql;
本文参考来源:
[1] https://www.cnblogs.com/zhuyongzhe/p/7686105.html