MySql查询语句集合

mysql用的最多的是查询操作，下面就总结一下mysql的常见查询语句。

基本查询结构：

-- 查询

默认数据库文件存放在： /var/lib/mysql

-- 数据库的操作

# 在linux终端：

启动：$ sudo service mysql start
停止：$ sudo service mysql stop
重启：$ sudo service mysql restart

-- 链接数据库

-- mysql -uroot -p密码

-- mysql -uroot -p

-- sql语句最后需要有分号;结尾

-- 显示数据库版本

select version();

-- 显示时间

select now();

-- 查看所有数据库

show databases;

-- 创建数据库

-- create database 数据库名 charset=utf8;

create database python_new_info;

create database python_new_info charset=utf8;

-- 查看创建数据库的语句

show create database python_new_info;

-- 查看当前使用的数据库

select database();

-- 使用数据库

-- use 数据库的名字

use python_new_info

-- 删除数据库

-- drop database 数据库名;

drop database python_new_info;

-- 数据表的操作

-- 查看当前数据库中所有表

show tables;

-- 创建表

-- auto_increment表示自动增长

-- 创建一个学生的数据表(id、name、age、high、gender、cls_id)

-- create table 表名(字段名类型名约束);

create table classes(

id int unsigned auto_increment primary key not null,

name varchar(20) not null

);

create table students (

id int unsigned auto_increment primary key not null,

name varchar(30) not null,

age tinyint unsigned default 0,

high decimal(5,2),

gender enum("男", "女", "中性", "保密") default "保密",

cls_id int unsigned

);

-- 查看表的创建语句

show create table classes;

show create table students;

-- 查看表结构

-- desc 数据表的名字;

desc students;

+--------+-------------------------------------+------+-----+---------+----------------+

+--------+-------------------------------------+------+-----+---------+----------------+

| id | int(10) unsigned | NO | PRI | NULL | auto_increment |

| age | tinyint(3) unsigned | YES | | 0 | |

| gender | enum('男','女','中性','保密') | YES | | 保密 | |

+--------+-------------------------------------+------+-----+---------+----------------+

-- 修改表-添加字段

-- alter table 表名 add 列名类型;

alter table students add birthday datetime;

-- 修改表-修改字段：不重命名版

-- alter table 表名 modify 列名类型及约束;

alter table students modify birthday date;

-- 修改表-修改字段：重命名版

-- alter table 表名 change 原名新名类型及约束;

alter table students change birthday birth date;

-- 修改表-删除字段

-- alter table 表名 drop 列名;

alter table students drop high;

-- 删除表

-- drop table 表名;

drop table students;

-- 增删改查(curd)

+-------+------------------+------+-----+---------+----------------+

+-------+------------------+------+-----+---------+----------------+

| id | int(10) unsigned | NO | PRI | NULL | auto_increment |

+-------+------------------+------+-----+---------+----------------+

+--------+-------------------------------------+------+-----+---------+----------------+

+--------+-------------------------------------+------+-----+---------+----------------+

| id | int(10) unsigned | NO | PRI | NULL | auto_increment |

| age | tinyint(3) unsigned | YES | | 0 | |

| gender | enum('男','女','中性','保密') | YES | | 保密 | |

+--------+-------------------------------------+------+-----+---------+----------------+

-- 增加

-- 全列插入

-- insert into 表名 values (...)

insert into classes values(0, "python_01");

insert into students values(0, "张三", 20, "男", 1, "1990-01-01");

-- 失败 insert into students values(0, "李四", 20, "不知道", 1, "1990-01-01");

insert into students values(0, "李四", 20, 1, 1, "1990-01-01");

-- 失败 insert into students values(0, "王二", 20, 5, 1, "1990-01-01");

-- 部分插入

-- insert into 表名(列1,...) values(值1,...)

insert into students (name) values ("李四");

insert into students (name, birth) values ("王二", "2008-08-08");

-- 多行插入

insert into students (name, birth) values ("刘备", "1000-08-08"),("张飞", "1000-08-08");

insert into students values (0, "张三1", 20, "男", 1, "1990-01-01"), (0, "张三2", 20, "男", 1, "1990-01-01");

-- 修改

-- update 表名 set 列1=值1,列2=值2... where 条件

update students set age=21;

update students set age=18 where id=1;

update students set age=10,gender=4 where id=1;

-- 删除

-- 物理删除

-- delete from 表名 where 条件;

delete from students where id=2;

-- 逻辑删除

-- 用一个字段来表示这条信息是否已经不能再使用了

alter table students add is_delete bit;

alter table students modify is_delete bit default 0;

update students set is_delete=0;

update students set is_delete=1 where id=5;

-- 查询基本使用

-- 查询所有列

-- select * from 表名;

select * from students;

-- 指定条件查询

-- select * from 表名 where xxxx;

select * from students where is_delete=1;

-- 查询指定列

-- select 列1,列2,... from 表名;

select name, gender from students;

-- 字段的顺序

select gender, name from students;

-- 可以使用as为列或表指定别名

-- select 列1【 as 名字】,列2【 as 名字】,... from 表名;

select name as 姓名, gender as 性别 from students;

-- 数据库的备份

在mysql 后台服务器开启的状态下：（linux终端）

$ mysqldump -uroot -p 数据库名 > 数据库名.sql # 导出备份，导出到当前文件夹下。root 为用户名

# 从外界导入列表到数据库

$ mysqldump -u用户名 -p 数据库名 < 数据库名.sql

# 在数据库内部导入外界当前登录路径下的列表数据

sourece sql文件名

在数据库内部添加．ｓｑｌ　文件－－－－－＞　source stock_db.sql　

进入数据库再输入，注意源文件一定要在登录数据库时的路径下。

查询：

-- 查询所有字段

-- select * from 表名;

select * from students;

-- 查询指定字段

-- select 列1,列2,... from 表名;

select name, gender from students;

-- 使用 as 给字段起别名

-- select 字段 as 名字.... from 表名;

select name as 姓名, gender as 性别 from students;

-- 可以通过 as 给表起别名

-- select 数据表别名.字段 .... from 表名 as 别名;

select name, gender from students as s;

select students.name, students.gender from students;

-- 失败select students.name, students.gender from students as s;

select s.name, s.gender from students as s;

-- 消除重复行

-- distinct 字段

select gender from students;

select distinct gender from students;

-- 条件查询

-- 比较运算符

-- >

-- 查询大于18岁的信息

select * from students where age>18;

-- <

-- 查询小于18岁的信息

-- >=

-- <=

-- 查询小于或者等于18岁的信息

select * from students where age<=18;

-- =

-- != 或者 <>

-- 逻辑运算符

-- and

-- 18岁以上的女性

select * from students where age>18 and gender=2;

-- or

-- 18以上或者身高查过180(包含)以上

select * from students where age>18 or height>=180;

-- not

-- 不在 18岁以上的女性这个范围内的信息

select * from students where age>18 and gender=2;

select * from students where not (age>18 and gender=2);

-- 模糊查询

-- like

-- %

-- 查询姓名中以 "小" 开始的名字

select name from students where name like "小%";

-- _

-- 查询有2个字的名字

select name from students where name like "__";

-- 查询有3个字的名字

select name from students where name like "___";

-- rlike 正则

-- 查询以周开始的姓名

select name from students where name rlike "^周";

select name from students where name rlike "^周.*伦$";

-- 范围查询

-- in表示在一个非连续的范围内

-- 查询年龄为18、34的姓名

select name from students where age in (18, 34);

select name, age from students where age in (18, 34);

-- not in 不非连续的范围之内

-- 年龄不是 18、34岁之间的信息

select name, age from students where age not in (18, 34);

-- between ... and ...表示在一个连续的范围内

-- 查询年龄在18到34之间的的信息

select * from students where age between 18 and 34;

-- not between ... and ...表示不在一个连续的范围内

-- 查询年龄不在在18到34之间的的信息

select * from students where age not between 18 and 34;

-- 失败select * from students where age not (between 18 and 34);

-- 空判断

-- 判空is null

-- 查询身高为空的信息

select * from students where height is null;

-- 判非空is not null

select * from students where height is not null;

-- 排序

-- order by 字段

-- asc从小到大排列，即升序

-- 查询年龄在18到34岁之间的男性，按照年龄从小到到排序

select * from students where (age between 18 and 34) and gender=1 order by age; # 优先使用

select * from students where (age between 18 and 34) and gender=1 order by age asc;

-- desc从大到小排序，即降序

-- 查询年龄在18到34岁之间的女性，身高从高到矮排序

select * from students where (age between 18 and 34) and gender=2 order by height desc;

-- order by 多个字段

-- 查询年龄在18到34岁之间的女性，身高从高到矮排序, 如果身高相同的情况下按照年龄从小到大排序

select * from students where (age between 18 and 34) and gender=2 order by height desc, age asc;

-- 查询年龄在18到34岁之间的女性，身高从高到矮排序, 如果身高相同的情况下按照年龄从小到大排序,

-- 如果年龄也相同那么按照id动大到小排序

select * from students where (age between 18 and 34) and gender=2 order by height desc, age asc, id desc;

-- 按照年龄从小到大、身高从高到矮的排序

select * from students order by age asc, height desc;

-- 聚合函数

-- 总数

-- count

-- 查询男性有多少人，女性有多少人

select count(*) as 男生的人数 from students where gender=1;

select count(*) as 女生的人数 from students where gender=2;

select count(name) as 女生的人数 from students where gender=2;

-- 最大值

-- max

-- 查询最大的年龄

select max(age) from students;

-- 查询女性的最高身高

select max(height) from students where gender=2;

-- 最小值

-- min

-- 求和

-- sum

-- 计算所有人的年龄总和

select sum(age) from students;

-- 平均值

-- avg

-- 计算平均年龄

select avg(age) from students;

-- 计算平均年龄 sum(age)/count(*)

select sum(age) / count(*) from students;

-- 四舍五入 round(123.23 , 1) 保留1位小数

-- 计算所有人的平均年龄，保留2位小数

select round(avg(age), 2) from students;

-- 计算男性的平均身高保留2位小数

select round(avg(age), 2) from students where gender=1;

-- 分组

-- group by

-- 按照性别分组

--失败select * from students group by gender;

select gender from students group by gender;

select name from students where gender=1;

-- 计算女性的人数

select count(*) as 女性的人数 from students where gender=2 group by gender;

-- 计算男性的人数

select count(*) as 男性的人数 from students where gender=1;

-- 查询所有的性别

select gender from students group by gender;

select distinct gender from students; # 去重

-- group_concat(...)

-- 查询同种性别中的姓名

select gender, group_concat(name) from students group by gender;

select gender, group_concat(name, age) from students group by gender;

-- 查询同种性别中的人数count(*)

select gender, count(*) from students group by gender;

-- having

-- 查询每种性别中的平均年龄avg(age)

select gender, avg(age) from students group by gender;

-- 查询平均年龄超过30岁的性别，以及姓名 having avg(age) > 30

select gender, group_concat(name) from students group by gender having avg(age)>30;

-- 分页

-- limit start, count

-- 查询前5个数据

select * from students limit 0,5;

-- 查询id4-8（包含）的书序

select * from students limit 3,5;

-- 每页显示2个，第1个页面

select * from students limit 0,2;----->每页的数量*(页数-1), 每页的数量

-- 每页显示2个，第2个页面

select * from students limit 2,2;

-- 每页显示2个，第3个页面

select * from students limit 4,2;

-- 每页显示2个，显示第4页的信息, 按照年龄从小到大排序

-- 失败select * from students limit 2*(4-1),2;

select * from students limit 6,2;

-- 失败select * from students limit 6,2 order by age asc;

select * from students order by age asc limit 6,2;

-- 链接查询

-- inner join ... on

-- 查询有能够对应班级的学生以及班级信息

select * from students inner join classes on students.cls_id=classes.id;

-- 按照要求显示字典

select students.name from students inner join classes on students.cls_id=classes.id;

-- 给数据表起名字

select s.name from students as s inner join classes as c on s.cls_id=c.id;

select s.*,c.name from students as s inner join classes as c on s.cls_id=c.id;

-- 在以上的查询中，将班级姓名显示在第1列

select c.name, s.* from students as s inner join classes as c on s.cls_id=c.id;

-- 查询有能够对应班级的学生以及班级信息, 按照班级进行排序

-- select c.xxx s.xxx from student as s inner join clssses as c on .... order by ....;

select c.name, s.* from students s inner join classes c on s.cls_id=c.id order by c.name;

-- left join

-- 查询每位学生对应的班级信息

select s.*, c.name from students as s left join classes as c on s.cls_id=c.id;

-- 查询没有对应班级信息的学生

-- select ... from xxx as s left join xxx as c on..... where .....

-- select ... from xxx as s left join xxx as c on..... having .....

select s.*, c.name from students as s left join classes as c on s.cls_id=c.id where c.name is null;

select s.*, c.name from students as s left join classes as c on s.cls_id=c.id having c.name is null;

-- right join

-- 将数据表名字互换位置，用left join完成

-- 自关联

-- 查询所有省份

select * from areas where pid is null;

-- 查询出山东省有哪些市

select * from areas as city inner join areas as province on city.pid=province.aid where province.atitle="山东省";

-- 查询出青岛市有哪些县城

select * from areas as city inner join areas as province on city.pid=province.aid where province.atitle="青岛市";

-- 子查询

-- 标量子查询

-- 查询出高于平均身高的信息

-- 失败select * from students height > avg(height);

-- 失败select * from students where height > select avg(height) from students;

select * from students where height > (select avg(height) from students);

-- 列子查询

-- 查询学生的班级号能够对应的学生信息

select * from students where cls_id in (1, 2);

select * from students where cls_id in (select id from classes);

子查询分类

标量子查询: 子查询返回的结果是一个数据(一行一列)
列子查询: 返回的结果是一列(一列多行)
行子查询: 返回的结果是一行(一行多列)

MySql查询语句集合

子查询分类

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