mysql的使用
— 数据库的操作
— 链接数据库
mysql -uroot -p
mysql -uroot -pmysql
— 退出数据库
exit/quit/ctrl+d
— 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 python04;
create database python04new charset=utf8;
— 查看创建数据库的语句
— show crate database ….
show create database python04;
— 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 python04new;
— 删除数据库
— drop database 数据库名;
drop database python04;
— 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
— not null 表示不能为空
— primary key 表示主键s
— default 默认值
— create table 数据表名字 (字段 类型 约束[, 字段 类型 约束]);
create table xxxxx(
id int, name varchar(30));
create table yyyyy(id int primary key not null auto_increment, name varchar(30));
create table zzzzz(
id int primary key not null auto_increment,
name varchar(30)
);
— 查看表结构
— desc 数据表的名字;
desc xxxxx;
— 创建students表(id、name、age、high、gender、cls_id)
create table students(
id int unsigned not null auto_increment primary key,
name varchar(30),
age tinyint unsigned default 0,
high decimal(5,2),
gender enum(“男”, “女”, “中性”, “保密”) default “保密”,
cls_id int unsigned
);
insert into students values(0, “老王”, 18, 188.88, “男”, 0);
insert into students values(0, “王小二”, 19, 150.12, “女”, 1);
insert into students values(0, “李爽”, 22, 165.00, “女”, 2);
insert into students values(0, “李杰”, 60, 158.10, “男”, 3);
insert into students values(0, “刘菲菲”, 12, 175.50, “女”, 4);
insert into students values(0, “小明”, 19, 161.30, “男”, 0);
insert into students values(0, “李蕾”, 16, 158.20, “女”, 1);
insert into students values(0, “韩没灭”, 25, 150.00, “男”, 2);
insert into students values(0, “杰克”, 36, 180.12, “女”, 3);
insert into students values(0, “路西”, 18, 183.12, “男”, 4);
insert into students values(0, “王静”, 12, 196.12, “中性”, 1);
insert into students values(0, “王姐”, 34, 188.12, “男”, 1);
insert into students values(0, “徐开心”, 35, 200.12, “女”, 2);
insert into students values(0, “江配”, 39, 196.12, “”, 3);
insert into students values(0, “盛淑星”, 26, 162.12, “女”, 4);
insert into students values(0, “邓程飞”, 19, 169.12, “男”, 5);
insert into students values(0, “江铃”, 18, 175.12, “女”, 6);
insert into students values(0, “唐世菊”, 13, 190.12, “男”, 1);
select * from students;
— 创建classes表(id、name)
create table classes(
id int unsigned not null auto_increment primary key,
name varchar(30)
gender enum(“男”, “女”, “中性”, “保密”) default “保密”
);
insert into classes values(0, “python04大神”);
select * from classes;
— 查看表的创建语句
— show create table 表名字;
show create table students;
— 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 default “2000-01-01”;
— 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 database 数据库;
— drop table 数据表;
drop table xxxxx;
— 增删改查(curd)
— 增加
— 全列插入
— insert [into] 表名 values(…)
— 主键字段 可以用 0 null default 来占位
— 向classes表中插入 一个班级
insert into classes values(0, “菜鸟班”);
+——–+————————————-+——+—–+————+—————-+
| Field | Type | Null | Key | Default | Extra |
+——–+————————————-+——+—–+————+—————-+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(30) | YES | | NULL | |
| age | tinyint(3) unsigned | YES | | 0 | |
| gender | enum(‘男’,’女’,’中性’,’保密’) | YES | | 保密 | |
| cls_id | int(10) unsigned | YES | | NULL | |
| birth | date | YES | | 2000-01-01 | |
+——–+————————————-+——+—–+————+—————-+
— 向students表插入 一个学生信息
insert into students values(0, “小李飞刀”, 20, “女”, 1, “1990-01-01”);
insert into students values(null, “小李飞刀”, 20, “女”, 1, “1990-01-01”);
insert into students values(default, “小李飞刀”, 20, “女”, 1, “1990-01-01”);
— 失败
— insert into students values(default, “小李飞刀”, 20, “第4性别”, 1, “1990-02-01”);
— 枚举中 的 下标从1 开始 1—“男” 2—>”女”….
insert into students values(default, “小李飞刀”, 20, 1, 1, “1990-02-01”);
— 部分插入
— insert into 表名(列1,…) values(值1,…)
insert into students (name, gender) values (“小乔”, 2);
— 多行插入
insert into students (name, gender) values (“大乔”, 2),(“貂蝉”, 2);
insert into students values(default, “西施”, 20, “女”, 1, “1990-01-01”), (default, “王昭君”, 20, “女”, 1, “1990-01-01”);
— 修改
— update 表名 set 列1=值1,列2=值2… where 条件;
update students set gender=1; — 全部都改
update students set gender=1 where name=”小李飞刀”; — 只要name是小李飞刀的 全部的修改
update students set gender=1 where id=3; — 只要id为3的 进行修改
update students set age=22, gender=1 where id=3; — 只要id为3的 进行修改
— 查询基本使用
— 查询所有列
— select * from 表名;
select * from students;
—定条件查询
select * from students where name=”小李飞刀”; — 查询 name为小李飞刀的所有信息
select * from students where id>3; — 查询 name为小李飞刀的所有信息
— 查询指定列
— select 列1,列2,… from 表名;
select name,gender from students;
— 可以使用as为列或表指定别名
— select 字段[as 别名] , 字段[as 别名] from 数据表 where ….;
select name as 姓名,gender as 性别 from students;
— 字段的顺序
select id as 序号, gender as 性别, name as 姓名 from students;
— 删除
— 物理删除
— delete from 表名 where 条件
delete from students; — 整个数据表中的所有数据全部删除
delete from students where name=”小李飞刀”;
— 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
— 给students表添加一个is_delete字段 bit 类型
alter table students add is_delete bit default 0;
update students set is_delete=1 where id=6;
— 数据的准备
— 创建一个数据库
create database python_test charset=utf8;
— 使用一个数据库
use python_test;
— 显示使用的当前数据是哪个?
select database();
— 创建一个数据表
— students表
create table students(
id int unsigned primary key auto_increment not null,
name varchar(20), –default ”,
age tinyint unsigned default 0,
height decimal(5,2),
gender enum(‘男’,’女’,’中性’,’保密’),– default ‘保密’,
cls_id int unsigned default 0,
is_delete bit default 0
);
— classes表
create table classes (
id int unsigned auto_increment primary key not null,
name varchar(30) not null
);
— 查询
— 查询所有字段
— select * from 表名;
select * from students;
select * from classes;
select id, name from classes;
— 查询指定字段
— select 列1,列2,… from 表名;
select name, age 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, age as 年龄 from students;
— select 表名.字段 …. from 表名;
select students.name, students.age from students;
— 可以通过 as 给表起别名
— select 别名.字段 …. from 表名 as 别名;
select students.name, students.age from students;
select s.name, s.age from students as s;
— 失败的select students.name, students.age from students as s;
— 消除重复行
— distinct 字段
select distinct gender from students;
— 条件查询
— 比较运算符
— select …. from 表名 where …..
— >
— 查询大于18岁的信息
select * from students where age>18;
select id,name,gender from students where age>18;
— <
— 查询小于18岁的信息
select * from students where age<18;
— >=
— <=
— 查询小于或者等于18岁的信息
— =
— 查询年龄为18岁的所有学生的名字
select * from students where age=18;
— != 或者 <>
— 逻辑运算符
— and
— 18到28之间的所以学生信息
select * from students where age>18 and age<28;
— 失败select * from students where age>18 and <28;
— 18岁以上的女性
select * from students where age>18 and gender=”女”;
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 not age>18 and gender=2;
select * from students where not (age>18 and gender=2);
— 年龄不是小于或者等于18 并且是女性
select * from students where (not age<=18) and gender=2;
— 模糊查询
— like
— % 替换1个或者多个
— _ 替换1个
— 查询姓名中 以 “小” 开始的名字
select name from students where name=”小”;
select name from students where name like “小%”;
— 查询姓名中 有 “小” 所有的名字
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 “__”;
— 查询至少有2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.*”;
— 查询以 周开始、伦结尾的姓名
select name from students where name rlike “^周.*伦$”;
— 范围查询
— in (1, 3, 8)表示在一个非连续的范围内
— 查询 年龄为18、34的姓名
select name,age from students where age=18 or age=34;
select name,age from students where age=18 or age=34 or age=12;
select name,age from students where age in (12, 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 (12, 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 name, age 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;
select * from students where not age between 18 and 34;
— 失败的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;
select * from students where height is NULL;
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
— desc从大到小排序，即降序
— 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;
select * from students where (age between 18 and 34) and gender=1 order by age;
select * from students where (age between 18 and 34) and gender=1 order by age asc;
— 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
;
— 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从大到小排序
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 * from students where gender=1;
select count(*) from students where gender=1;
select count(*) as 男性人数 from students where gender=1;
select count(*) as 女性人数 from students where gender=2;
— 最大值
— max
— 查询最大的年龄
select age from students;
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(sum(age)/count(*), 2) from students;
select round(sum(age)/count(*), 3) from students;
— 计算男性的平均身高 保留2位小数
select round(avg(height), 2) from students where gender=1;
— select name, round(avg(height), 2) from students where gender=1;
— 分组
— group by
— 按照性别分组,查询所有的性别
select name from students group by gender;
–select * from students group by gender;
select gender from students group by gender;
— 失败select * from students group by gender;
— 计算每种性别中的人数
select gender,count(*) from students group by gender;
— 计算男性的人数
select gender,count(*) from students where gender=1 group by gender;
— group_concat(…)
— 查询同种性别中的姓名
select gender,group_concat(name) from students where gender=1 group by gender;
select gender,group_concat(name, age, id) from students where gender=1 group by gender;
select gender,group_concat(name, “_”, age, ” “, id) from students where gender=1 group by gender;
— having
— 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),avg(age) from students group by gender having avg(age)>30;
— 查询每种性别中的人数多于2个的信息
select gender, group_concat(name) from students group by gender having count(*)>2;
— 分页
— limit start, count
— 限制查询出来的数据个数
select * from students where gender=1 limit 2;
— 查询前5个数据
select * from students limit 0, 5;
— 查询id6-10（包含）的书序
select * from students limit 5, 5;
— 每页显示2个，第1个页面
select * from students limit 0,2;
— 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，第4个页面
select * from students limit 6,2; — —–> limit (第N页-1)*每个的个数, 每页的个数;
— 每页显示2个，显示第6页的信息, 按照年龄从小到大排序
— 失败select * from students limit 2*(6-1),2;
— 失败select * from students limit 10,2 order by age asc;
select * from students order by age asc limit 10,2;
select * from students where gender=2 order by height desc limit 0,2;
— 连接查询
— inner join … on
— select … from 表A inner join 表B;
select * from students inner join classes;
— 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;
— 按照要求显示姓名、班级
select students.*, classes.name from students inner join classes on students.cls_id=classes.id;
select students.name, classes.name from students inner join classes on students.cls_id=classes.id;
— 给数据表起名字
select s.name, c.name 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，显示学生的所有信息，只显示班级名称
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 as s inner join classes as c on s.cls_id=c.id order by c.name;
— 当时同一个班级的时候，按照学生的id进行从小到大排序
select c.name, s.* from students as s inner join classes as c on s.cls_id=c.id order by c.name,s.id;
— left join
— 查询每位学生对应的班级信息
select * 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 * from students as s left join classes as c on s.cls_id=c.id having c.id is null;
select * from students as s left join classes as c on s.cls_id=c.id where c.id is null;
— right join on
— 将数据表名字互换位置，用left join完成
— 自关联
— 省级联动 url:http://demo.lanrenzhijia.com/2014/city0605/
— 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 province inner join areas as city on city.pid=province.aid having province.atitle=”山东省”;
select province.atitle, city.atitle from areas as province inner join areas as city on city.pid=province.aid having province.atitle=”山东省”;
— 查询出青岛市有哪些县城
select province.atitle, city.atitle from areas as province inner join areas as city on city.pid=province.aid having province.atitle=”青岛市”;
select * from areas where pid=(select aid from areas where atitle=”青岛市”;
— 子查询
— 标量子查询
— 查询出高于平均身高的信息
— 查询最高的男生信息
select * from students where height = 188;
select * from students where height = (select max(height) from students);
— 列级子查询
— 查询学生的班级号能够对应的学生信息
— select * from students where cls_id in (select id from classes);
— 数据的准备
— 创建一个数据库
create database python_test charset=utf8;
— 使用一个数据库
use python_test;
— 显示使用的当前数据是哪个?
select database();
— 创建一个数据表
— students表
create table students(
id int unsigned primary key auto_increment not null,
name varchar(20), –default ”,
age tinyint unsigned default 0,
height decimal(5,2),
gender enum(‘男’,’女’,’中性’,’保密’),– default ‘保密’,
cls_id int unsigned default 0,
is_delete bit default 0
);
— classes表
create table classes (
id int unsigned auto_increment primary key not null,
name varchar(30) not null
);
— 查询
— 查询所有字段
— select * from 表名;
select * from students;
select * from classes;
select id, name from classes;
— 查询指定字段
— select 列1,列2,… from 表名;
select name, age 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, age as 年龄 from students;
— select 表名.字段 …. from 表名;
select students.name, students.age from students;
— 可以通过 as 给表起别名
— select 别名.字段 …. from 表名 as 别名;
select students.name, students.age from students;
select s.name, s.age from students as s;
— 失败的select students.name, students.age from students as s;
— 消除重复行
— distinct 字段
select distinct gender from students;
— 条件查询
— 比较运算符
— select …. from 表名 where …..
— >
— 查询大于18岁的信息
select * from students where age>18;
select id,name,gender from students where age>18;
— <
— 查询小于18岁的信息
select * from students where age<18;
— >=
— <=
— 查询小于或者等于18岁的信息
— =
— 查询年龄为18岁的所有学生的名字
select * from students where age=18;
— != 或者 <>
— 逻辑运算符
— and
— 18到28之间的所以学生信息
select * from students where age>18 and age<28;
— 失败select * from students where age>18 and <28;
— 18岁以上的女性
select * from students where age>18 and gender=”女”;
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 not age>18 and gender=2;
select * from students where not (age>18 and gender=2);
— 年龄不是小于或者等于18 并且是女性
select * from students where (not age<=18) and gender=2;
— 模糊查询
— like
— % 替换1个或者多个
— _ 替换1个
— 查询姓名中 以 “小” 开始的名字
select name from students where name=”小”;
select name from students where name like “小%”;
— 查询姓名中 有 “小” 所有的名字
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 “__”;
— 查询至少有2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.*”;
— 查询以 周开始、伦结尾的姓名
select name from students where name rlike “^周.*伦$”;
— 范围查询
— in (1, 3, 8)表示在一个非连续的范围内
— 查询 年龄为18、34的姓名
select name,age from students where age=18 or age=34;
select name,age from students where age=18 or age=34 or age=12;
select name,age from students where age in (12, 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 (12, 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 name, age 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;
select * from students where not age between 18 and 34;
— 失败的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;
select * from students where height is NULL;
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
— desc从大到小排序，即降序
— 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;
select * from students where (age between 18 and 34) and gender=1 order by age;
select * from students where (age between 18 and 34) and gender=1 order by age asc;
— 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
;
— 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从大到小排序
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 * from students where gender=1;
select count(*) from students where gender=1;
select count(*) as 男性人数 from students where gender=1;
select count(*) as 女性人数 from students where gender=2;