博观而约取,厚积而薄发。
数据库操作
连接数据库
mysql -uroot -p
退出数据库
exit
quit
ctrl+d
显示时间
select now();
+---------------------+
| now() |
+---------------------+
| 2020-06-09 22:13:43 |
+---------------------+
1 row in set (0.02 sec)
显示版本
select version();
+-----------+
| version() |
+-----------+
| 5.7.21-1 |
+-----------+
1 row in set (0.00 sec)
查看数据库
show databases;
创建数据库，指定编码utf8
create database xxx charset=utf8;
显示创建数据库
show create database db_name;
+----------+---------------------------------------------------------------+
| Database | Create Database |
+----------+---------------------------------------------------------------+
| demo | CREATE DATABASE `demo` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+---------------------------------------------------------------+
1 row in set (0.00 sec)
查看当前数据库
select database();
+------------+
| database() |
+------------+
| demo |
+------------+
1 row in set (0.00 sec)
切换数据库
use db_nmae;
删除数据库
drop database db_name;
表操作
查看当前数据库的所有表
show tables;
+----------------+
| Tables_in_demo |
+----------------+
| tb_name |
+----------------+
1 row in set (0.00 sec)
创建表
create table tb_name(id int primary key ,name varchar (20));
查看表结构
desc tb_name;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
显示创建表
show create table tb_name;
+---------+------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+---------+------------------------------------------------------------------------------------------------------------------------------------------------+
| tb_name | CREATE TABLE `tb_name` (
`id` int(11) NOT NULL,
`name` varchar(20) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+---------+------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
创建一个学生表
create table stu(
id int unsigned not null auto_increment primary key ,
name varchar (20),
age tinyint unsigned,
high decimal (5,2),
gender enum("男","女","保密","中性") default "保密",
cls_id int unsigned
);
创建班级表
create table class(
id int unsigned not null primary key auto_increment,
name varchar (30)
);
插入学生数据
insert into stu values (0,"ydy",22,172.00,"男",0);
查看学生所有数据
select * from stu;
+----+------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
+----+------+------+--------+--------+--------+
1 row in set (0.00 sec)
学生表添加字段
alter table stu add birthday datetime;
+----------+-------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------------------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
| high | decimal(5,2) | YES | | NULL | |
| gender | enum('男','女','保密','中性') | YES | | 保密 | |
| cls_id | int(10) unsigned | YES | | NULL | |
| birthday | datetime | YES | | NULL | |
+----------+-------------------------------------+------+-----+---------+----------------+
7 rows in set (0.00 sec)
修改字段-不重命名
alter table stu modify birthday date ;
+----------+-------------------------------------+------+-----+---------+----------------+
| birthday | date | YES | | NULL | |
+----------+-------------------------------------+------+-----+---------+----------------+
7 rows in set (0.00 sec)
修改字段-重命名
alter table stu change birthday birth date default "2019-02-24";
+--------+-------------------------------------+------+-----+------------+----------------+
| birth | date | YES | | 2019-02-24 | |
+--------+-------------------------------------+------+-----+------------+----------------+
7 rows in set (0.00 sec)
删除字段
alter table stu drop high;
+--------+-------------------------------------+------+-----+------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------------------------------+------+-----+------------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
| gender | enum('男','女','保密','中性') | YES | | 保密 | |
| cls_id | int(10) unsigned | YES | | NULL | |
| birth | date | YES | | 2019-02-24 | |
+--------+-------------------------------------+------+-----+------------+----------------+
6 rows in set (0.00 sec)
删除表
drop table stu;
排序
order by：小－>大asc：小->大desc：大->小
mysql> select * from stu;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
| 7 | xiaohua | 15 | 160.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
7 rows in set (0.00 sec)
查询年龄18-34之间的男性,按照年龄由小到大
select * from stu where (age between 18 and 34) and gender=1 order by age;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
+----+----------+------+--------+--------+--------+
4 rows in set (0.03 sec)
年龄在18-34之间女性，身高由高到低
select * from stu where (age between 18 and 34) and gender=2 order by high desc ;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
2 rows in set (0.00 sec)
年龄在18-34之间女性，身高由高到低 ,身高相同按照id由小到大
select * from stu where (age between 18 and 34) and gender=2 order by high desc,id desc ;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
2 rows in set (0.00 sec)
分页
limit start,count
mysql> select * from stu;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
| 7 | xiaohua | 15 | 160.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
7 rows in set (0.00 sec)
限制查询出来的数据个数
select * from stu where gender=1 limit 2;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
+----+----------+------+--------+--------+--------+
2 rows in set (0.00 sec)
查询前5个数据
select * from stu limit 0,5;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
5 rows in set (0.00 sec)
查询6-10的数据
select * from stu limit 5,5;
+----+---------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+---------+------+--------+--------+--------+
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
| 7 | xiaohua | 15 | 160.00 | 女 | 0 |
+----+---------+------+--------+--------+--------+
2 rows in set (0.00 sec)
每页显示两个，显示第二页信息，按照年龄从小到大排序
select * from stu order by age asc limit 2,2;
# 按年龄排序的结果：
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 7 | xiaohua | 15 | 160.00 | 女 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
+----+----------+------+--------+--------+--------+
7 rows in set (0.00 sec)
# 最终的结果
+----+--------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+--------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
+----+--------+------+--------+--------+--------+
2 rows in set (0.00 sec)
聚合函数
mysql> select * from stu;
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
| 7 | xiaohua | 15 | 160.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
7 rows in set (0.00 sec)
总数 count：查询男性有多少人
select count(*) from stu where gender=1;
+----------+
| count(*) |
+----------+
| 4 |
+----------+
1 row in set (0.00 sec)
最大值 max：查询最大年龄
select max(age) from stu;
+----------+
| max(age) |
+----------+
| 27 |
+----------+
1 row in set (0.00 sec)
最小值 min：身高最矮的女性
select min(high) from stu where gender=2;
+-----------+
| min(high) |
+-----------+
| 160.00 |
+-----------+
1 row in set (0.00 sec)
求和 sum：计算所有人的年龄总和
select sum(age) from stu ;
+----------+
| sum(age) |
+----------+
| 154 |
+----------+
1 row in set (0.00 sec)
平均值 avg：计算平均年龄
select avg(age) from stu;
select sum(age)/count(*) from stu ;
+----------+
| avg(age) |
+----------+
| 22.0000 |
+----------+
1 row in set (0.00 sec)
四舍五入round(123.45,2) 保留两位小数, 计算男性的平均身高，保留两位
select round(avg(high),2) from stu where gender=1;
+--------------------+
| round(avg(high),2) |
+--------------------+
| 173.25 |
+--------------------+
1 row in set (0.00 sec)
分组
+----+----------+------+--------+--------+--------+
| id | name | age | high | gender | cls_id |
+----+----------+------+--------+--------+--------+
| 1 | ydy | 22 | 172.00 | 男 | 0 |
| 2 | zhangsan | 18 | 172.00 | 男 | 0 |
| 3 | lisi | 27 | 172.00 | 男 | 0 |
| 4 | wanger | 25 | 177.00 | 男 | 0 |
| 5 | xiaohong | 25 | 165.00 | 女 | 0 |
| 6 | xiaoli | 22 | 160.00 | 女 | 0 |
| 7 | xiaohua | 15 | 160.00 | 女 | 0 |
+----+----------+------+--------+--------+--------+
7 rows in set (0.00 sec)
group by：按照性别分组,查询所有的性别
select gender from students group by gender;
+--------+
| gender |
+--------+
| 男 |
| 女 |
+--------+
2 rows in set (0.00 sec)
# 计算每种性别的人数
select gender,count(*) from stu group by gender;
+--------+----------+
| gender | count(*) |
+--------+----------+
| 男 | 4 |
| 女 | 3 |
+--------+----------+
2 rows in set (0.00 sec)
group_concat()：查询同种性别中的姓名
select gender,group_concat(name) from stu group by gender;
+--------+--------------------------+
| gender | group_concat(name) |
+--------+--------------------------+
| 男 | ydy,zhangsan,lisi,wanger |
| 女 | xiaohong,xiaoli,xiaohua |
+--------+--------------------------+
2 rows in set (0.02 sec)
***************************************************************************
select gender,group_concat(name," ",age," ",id) from stu group by gender;
+--------+----------------------------------------------+
| gender | group_concat(name," ",age," ",id) |
+--------+----------------------------------------------+
| 男 | ydy 22 1,zhangsan 18 2,lisi 27 3,wanger 25 4 |
| 女 | xiaohong 25 5,xiaoli 22 6,xiaohua 15 7 |
+--------+----------------------------------------------+
2 rows in set (0.00 sec)
having：从查询的结果中获得东西
- 查询平均年龄超过30岁的性别，以及姓名
select gender,group_concat(name," ",age),avg(age) from students group by gender having avg(age)>30;
+--------+--------------------------------------+----------+
| gender | group_concat(name," ",age) | avg(age) |
+--------+--------------------------------------+----------+
| 男 | ydy 22,zhangsan 18,lisi 27,wanger 25 | 23.0000 |
| 女 | xiaohong 25,xiaoli 22,xiaohua 15 | 20.6667 |
+--------+--------------------------------------+----------+
2 rows in set (0.00 sec)
- 查询每种性别中的人数多余2个的信息
select gender,group_concat(name) from students group by gender having count(*)>2;
+--------+--------------------------+
| gender | group_concat(name) |
+--------+--------------------------+
| 男 | ydy,zhangsan,lisi,wanger |
| 女 | xiaohong,xiaoli,xiaohua |
+--------+--------------------------+
2 rows in set (0.00 sec)
视图
创建视图
# 查询地区关联的国家
select c.*,t.country_name from city as c ,country as t where c.country_id=t.country_id;
+---------+-----------+------------+--------------+
| city_id | city_name | country_id | country_name |
+---------+-----------+------------+--------------+
| 1 | 西安 | 1 | China |
| 2 | NewYork | 2 | America |
| 3 | 北京 | 1 | China |
| 4 | 上海 | 1 | China |
| 5 | 武汉 | 1 | China |
+---------+-----------+------------+--------------+
5 rows in set (0.00 sec)
# 创建视图
create view view_city_country as select c.*,t.country_name from city as c ,country as t where c.country_id=t.country_id;
查询视图数据
select * from view_city_country;
更新视图数据，视图建立关联的表也改变了，不建议使用
update view_city_country set xxx='xxx' where id=xxx;
修改视图
alter view view_city_country as select * from xxx where xxx=xxx;
查看视图
show create view view_city_country;
*************************** 1. row ***************************
View: view_city_country
Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `view_city_country` AS select `c`.`city_id` AS `city_id`,`c`.`city_name` AS `city_name`,`c`.`country_id` AS `country_id`,`t`.`country_name` AS `country_name` from (`city` `c` join `country` `t`) where (`c`.`country_id` = `t`.`country_id`)
character_set_client: utf8
collation_connection: utf8_general_ci
1 row in set (0.01 sec)
删除视图
# if exists：表示如果存在就删除
drop view if exists view_city_country;
索引
+---------+-----------+------------+
| city_id | city_name | country_id |
+---------+-----------+------------+
| 1 | 西安 | 1 |
| 2 | NewYork | 2 |
| 3 | 北京 | 1 |
| 4 | 上海 | 1 |
| 5 | 武汉 | 1 |
+---------+-----------+------------+
5 rows in set (0.00 sec)
+------------+--------------+
| country_id | country_name |
+------------+--------------+
| 1 | China |
| 2 | America |
| 3 | Japan |
| 4 | UK |
+------------+--------------+
4 rows in set (0.00 sec)
创建索引
create [UNIQUE|FULLTEXT|SPATIAL] index index_name [USING index_type]
on tbl_name(index_col_name)
index_name:索引名称
tbl_name：表名
index_col_name：字段名
# 例如：为学生表的姓名字段创建索引
create index idx_city_name on city(city_name);
创建复合索引
create index index_name on tb_name(字段1,字段2,字段3...);
查看索引
show index from students;
show index from studentsG;
+-------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| city | 0 | PRIMARY | 1 | city_id | A | 5 | NULL | NULL | | BTREE | | |
| city | 1 | idx_city_name | 1 | city_name | A | 5 | NULL | NULL | | BTREE | | |
+-------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
2 rows in set (0.00 sec)
删除索引
drop index idx_city_name on city;
ALTER添加索引
# 添加主键索引，值唯一，不能为NULL
alter table tb_name add primary key(column_list);
# 创建值唯一索引，可以为NULL且可以存在多个NULL
alter table tb_name add unique index_name(column_list);
# 普通索引
alter table tb_name add index index_name(column_list);
# 全文索引
alter table tb_name add fulltext index_name(column_list);
存储过程和函数
函数：一个有返回值的过程
过程：一个没有返回值的函数
修改mysql默认分号结尾执行语句
delimiter $
创建存储过程
# 此处的$是更改了默认分号结尾
create procedure procedure_name()
begin
-- SQL语句
end$
# 例如：
mysql> create procedure test()
-> begin
-> select 'hello';
-> end$
调用存储过程
# 此处的$是更改了默认分号结尾
call test()$
+-------+
| hello |
+-------+
| hello |
+-------+
1 row in set (0.02 sec)
查看存储过程
# 查询db_name数据库中的所有存储过程
# 此处的$是更改了默认分号结尾
select name from mysql.proc where db = 'db_name'$
+------+
| name |
+------+
| test |
+------+
1 row in set (0.02 sec)
show procedure statusG$
# 查看存储过程的定义，即当时创建使用的语法
show create procedure testG$
*************************** 1. row ***************************
Procedure: test
sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
Create Procedure: CREATE DEFINER=`root`@`localhost` PROCEDURE `test`()
begin
select 'hello';
end
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: utf8_general_ci
1 row in set (0.00 sec)
删除存储过程
# 此处的$是更改了默认分号结尾
drop procedure test$
存储过程语法
存储过程是可以编程的，意味这可以使用变量，表达式，控制结构，来完成比较复杂的功能。
变量
DECLARE variable_name [,variable_name...] datatype [DEFAULT value];
其中，datatype 为 MySQL 的数据类型，如: int, float, date,varchar(length)
declare：定义变量
mysql> create procedure pro_test()
-> begin
-> declare num int default 10;
-> select concat('num的值为:',num); # 打印
-> end$
# 调用
call pro_test()$
+-----------------------------+
| concat('num的值为:',num) |
+-----------------------------+
| num的值为:10 |
+-----------------------------+
1 row in set (0.00 sec)
set：设置变量
# 方式一
mysql> create procedure pro_test2()
-> begin
-> declare num int default 10;
-> set num = num + 10;
-> select num;
-> end$
call pro_test2()$
+------+
| num |
+------+
| 20 |
+------+
1 row in set (0.00 sec)
# 方式二
mysql> create procedure pro_test3()
-> begin
-> declare num int;
-> select count(*) into num from city;
-> select concat('city表中的记录数:',num);
-> end$
call pro_test3()$
+---------------------------------------+
| concat('city表中的记录数:',num) |
+---------------------------------------+
| city表中的记录数:5 |
+---------------------------------------+
1 row in set (0.00 sec)
if条件判断
根据定义的身高变量，判断当前身高所属的身材。
180及以上－－－－>高
170-180－－－－>标准
170以下－－－－>矮
create procedure pro_test4()
begin
declare height int default 175;
declare description varchar(50) default '';
if height>=180 then
set description='高';
elseif height>=170 and height<180 then
set description='标准';
else
set description='矮';
end if;
select concat('身高：',height,'身材：',description);
end$
call pro_test4()$
+----------------------------------------------------+
| concat('身高：',height,'身材：',description) |
+----------------------------------------------------+
| 身高：175身材：标准 |
+----------------------------------------------------+
1 row in set (0.00 sec)
传递参数
- in：输入参数
- out：输出参数，相当于返回值
- inout：既可以是输入参数，又可以是输出参数
create procedure pro_test5(in height int)
begin
declare description varchar(50) default '';
if height>=180 then
set description='高';
elseif height>=170 and height<180 then
set description='标准';
else
set description='矮';
end if;
select concat('身高：',height,'身材：',description);
end$
call pro_test5(198)$
+----------------------------------------------------+
| concat('身高：',height,'身材：',description) |
+----------------------------------------------------+
| 身高：198身材：高 |
+----------------------------------------------------+
1 row in set (0.00 sec)
# 传入参数height，返回description
create procedure pro_test6(in height int,out description varchar(10))
begin
if height>=180 then
set description='高';
elseif height>=170 and height<180 then
set description='标准';
else
set description='矮';
end if;
end;
call pro_test6(188,@description)$ # 值返回到了`@description`，@表示用户会话变量，仅用于当前会话
select @description$
+--------------+
| @description |
+--------------+
| 高 |
+--------------+
1 row in set (0.00 sec)
case结构
给定一个月份，计算所在的季度
create procedure pro_test7(in mon int)
begin
declare result varchar(10);
case
when mon >= 1 and mon <= 3 then
set result = '第一季度';
when mon >= 4 and mon <= 6 then
set result = '第二季度';
when mon >= 7 and mon <= 9 then
set result = '第三季度';
else
set result = '第四季度';
end case;
select concat('月份：', mon, '季度：', result);
end$
call pro_test7(1)$
+--------------------------------------------+
| concat('月份：',mon,'季度：',result) |
+--------------------------------------------+
| 月份：1季度：第一季度 |
+--------------------------------------------+
1 row in set (0.00 sec)
while循环
计算从1加到n的值
create procedure pro_test8(in n int)
begin
declare sum int default 0;
declare num int default 1;
while num <= n
do
set sum = sum + num;
set num = num + 1;
end while;
select sum;
end$
call pro_test8(4)$
+------+
| sum |
+------+
| 10 |
+------+
1 row in set (0.00 sec)
repeat循环
满足条件退出循环
create procedure pro_test9(in n int)
begin
declare sum int default 0;
repeat
set sum = sum + n;
set n = n - 1;
until n = 0 end repeat; # until满足退出循环
select sum;
end$
call pro_test9(3)$
+------+
| sum |
+------+
| 6 |
+------+
1 row in set (0.00 sec)
loop循环
leave语句退出循环
create procedure pro_test10(in n int)
begin
declare sum int default 0;
# c 是循环的别名
c:loop
set sum = sum + n;
set n = n - 1;
if n <=0 then
leave c;
end if;
end loop c;
select sum;
end;
call pro_test10(10)$
+------+
| sum |
+------+
| 55 |
+------+
1 row in set (0.00 sec)
游标
用来存储查询结果集的，便于遍历结果集
create procedure pro_test11()
begin
declare c_id int(11);
declare c_name varchar(50);
declare c_country_id int(11);
declare city_result cursor for select * from city;
open city_result;
# fetch 几次打印几次，当次数操作查询总数，最后报错
fetch city_result into c_id,c_name,c_country_id;
select concat('id=', c_id, 'name=', c_name, 'country_id', c_country_id);
fetch city_result into c_id,c_name,c_country_id;
select concat('id=', c_id, 'name=', c_name, 'country_id', c_country_id);
close city_result;
end;
call pro_test11()$
+------------------------------------------------------------------+
| concat('id=', c_id, 'name=', c_name, 'country_id', c_country_id) |
+------------------------------------------------------------------+
| id=1name=西安country_id1 |
+------------------------------------------------------------------+
1 row in set (0.00 sec)
+------------------------------------------------------------------+
| concat('id=', c_id, 'name=', c_name, 'country_id', c_country_id) |
+------------------------------------------------------------------+
| id=2name=NewYorkcountry_id2 |
+------------------------------------------------------------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
- 循环版本
create procedure pro_test12()
begin
declare c_id int(11);
declare c_name varchar(50);
declare c_country_id int(11);
declare has_data int default 1;
declare city_result cursor for select * from city;
# 当抓取不到数据,把has_data设置为0,循环退出
# 此句必须卸载游标声明之后
declare exit handler for not found set has_data = 0;
open city_result;
repeat
fetch city_result into c_id,c_name,c_country_id;
select concat('id=', c_id, 'name=', c_name, 'country_id', c_country_id);
until has_data = 0 end repeat;
close city_result;
end;
存储函数
定义一个存储函数，返回满足查询条件的的总记录数
create function func_test(countryId int)
returns int
begin
declare cnum int;
select count(*) into cnum from city where country_id = countryId;
return cnum;
end;
# 调用
select func_test(2)$
+--------------+
| func_test(2) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)
触发器
触发器是与表有关的数据库对象，指在insert/update/delete之前或之后触发并执行触发器中定义的SQL语句。触发器的这种特性由于应用在数据库端确保数据的完整性，日志记录，数据校验等操作。
- 创建日志表
create table city_logs
(
id int(11) not null auto_increment,
operation varchar(20) not null comment '操作类型，insert/update/delete',
operate_time datetime not null comment '操作时间',
operate_id int(11) not null comment '操作表id',
operate_params varchar(500) comment '操作参数',
primary key (id)
) engine = innodb
default charset = utf8$
创建触发器
通过触发器记录city表的变化日志
create trigger city_insert_trigger
# 插入之后触发
after insert
# 触发关联的表
on city
# 行级
for each row
begin
insert into city_logs(id, operation, operate_time, operate_id, operate_params)
values (null, 'insert', now(), NEW.city_id,
concat('插入后数据为:(id:', NEW.city_id, ',name:', NEW.city_name, ',country_id:', NEW.country_id, ')'));
end;
insert into `city` (`city_id`, `city_name`, `country_id`) value (6, '深圳', 1)$
# 插入完成之后查询city_logs
select * from city_logs$
+----+-----------+---------------------+------------+----------------------------------------------------+
| id | operation | operate_time | operate_id | operate_params |
+----+-----------+---------------------+------------+----------------------------------------------------+
| 1 | insert | 2020-06-10 16:37:17 | 6 | 插入后数据为:(id:6,name:深圳,country_id:1) |
+----+-----------+---------------------+------------+----------------------------------------------------+
1 row in set (0.00 sec)
查看触发器
show triggersG$
*************************** 1. row ***************************
Trigger: city_insert_trigger
Event: INSERT
Table: city
Statement: begin
insert into city_logs(id, operation, operate_time, operate_id, operate_params)
values (null, 'insert', now(), NEW.city_id,
concat('插入后数据为:(id:', NEW.city_id, ',name:', NEW.city_name, ',country_id:', NEW.country_id, ')'));
end
Timing: AFTER
Created: 2020-06-10 16:35:53.32
sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: utf8_general_ci
1 row in set (0.00 sec)
删除触发器
drop trigger xxxx;
事务
# 开启事务
begin/start transaction
# 提交事务
commit
# 回滚事务
rollback
与Python交互
from pymysql import *
def main():
# 创建Connection链接
conn = connect(host="localhost", port=3306,
database="jing_dong", user="root", password="root", charset="utf8")
# 获得Cursor对象
cs = conn.cursor()
count = cs.execute('select * from goods')
# 打印受影响的行数
print(count)
print(cs.fetchall())
# 增加
# count2 = cs.execute('insert into goods_cates(name) values ("硬盘")')
# 更新
# cs.execute('update goods_cates set name="机械硬盘" where name="硬盘"')
# 删除
# cs.execute('delete from goods_cates where name="机械硬盘"')
# 提交之前的操作，如果之前已经之执行过多次的execute，那么就都进行提交
conn.commit()
# 关闭Cursor对象
cs.close()
# 关闭Connection对象
conn.close()
if __name__ == '__main__':
main()