Embedded database development programming MySQL (full)

一、mysql

sudo apt-get install mysql-server mysql-client libmysqlclient-dev

-- 登录MYSQL
mysql -u root -p

-- 查看所有的数据库
show databases;

-- 使用数据库
use mysql;
-- 查看所有表
show tables;
-- 查看所有用户信息
select user from user;

-- 创建用户
create user "c++class"@"localhost" identified by "123456";

-- 修改密码
set password for "c++class"@"localhost" = PASSWORD("666666");

-- 授予权限
grant select on *.* to "c++class"@"localhost";
grant all on *.* to "c++class"@"localhost";

-- 创建表
create table int_test(
tiny_int tinyint,
small_int smallint,
medium_int mediumint,
commint_int int,
big_int bigint
);
-- 显示表的结构
describe int_test;

-- 插入数据
insert into int_test values(1,1,1,1,1);
insert into int_test values(200,1,1,1,1);  -- ERROR 1264 (22003): Out of range value for column 'tiny_int' at row 1
insert into int_test values(1,1,1,'a',1);  -- ERROR 1366 (HY000): Incorrect integer value: 'a' for column 'commint_int' at row 1

-- 创建学生表
create table student(
name varchar(10) not null,
age tinyint unsigned not null,
sex char(6)
);

-- 修改表
alter table student rename stu;
alter table stu drop sex;
alter table stu add sex char(6);
alter table stu add id int unsigned not null primary key auto_increment first;
alter table stu add birth date after name;
alter table stu add tel char(11) default '-';

-- 插入数据
insert into stu (id,name,birth,age,sex,tel) values(1000,"zhangsan","1999-9-9",90,"femal","11111111111");
insert into stu (name,birth,age,sex,tel) values("lisi","1993-9-19",40,"mal","22222222222");
insert into stu values(1002,"xiaozhang","1939-9-9",90,"femal","11213141511"),(1003,"xiaoming","1979-9-19",80,"femal","55555555555");
insert into stu (id,name,birth,age,sex) values(1005,"xiaowang","1993-9-19",40,"mal");
insert into stu (id,name,birth,age,sex) values(1005,"xiaowang","1993-9-19",40,"mal");
insert into stu stu values(1006,"张三","1998-8-8",21,"male","11111111111");

-- 查询数据
select * from stu;
select name from stu;
select name from stu where id > 1002;
select name from stu where id between 1001 and 1004;

-- 修改字符集
alter table stu convert to character set utf8;

-- 修改数据
update stu set tel = "88888888888" where name = "张三";

-- 删除记录
delete from stu where id = 1000;

-- 删除数据库
drop database test;

-- 创建数据库
create database test;

-- 事务操作
-- 创建表
create table account(
id int unsigned not null primary key,
name varchar(20),
money int
)charset utf8;

--插入数据
insert into account values(1000,"xiaozhang",2000),(1001,"xiaoming",5000),(1002,"张三",1000);

-- Xiao Zhang transfers money to Xiao Ming500
update account set money = money - 500 where id = 1000;

-- 停电了 数据出错

-- 开启事务
start transaction;

-- Xiao Zhang transfers money to Xiao Ming500
update account set money = money - 500 where id = 1000;

-- Xiao Ming increased500块
update account set money = money + 500 where id = 1001;

-- 提交
commit;



-- 开启事务
start transaction;

-- xiaozhang转出500
update account set money = money - 500 where id = 1000;

-- 设置回滚点
savepoint sp1;

-- Xiao Ming transferred out500块
update account set money = money - 500 where id = 1001;

-- 设置回滚点
savepoint sp2;

-- 张三增加1000块
update account set money = money + 1000 where id = 1002;

-- 回滚到sp1;
rollback to sp1;

-- 提交
commit;

二、Linux C下MYSQL的API

#include <iostream>
#include <mysql/mysql.h>
#include <iomanip>
using namespace std;

MYSQL *Init()
{
    MYSQL *m;
    m = mysql_init(NULL); //创建mysqlobject and initialized,返回对象的地址
    if (NULL == m)
    {
        cout<<mysql_error(m)<<endl; //打印错误信息
        return NULL;
    }
    m = mysql_real_connect(m,"localhost","c++class","1","mysql",0,NULL,0);
    if (NULL == m)
    {
        cout<<mysql_error(m)<<endl; //打印错误信息
        return NULL;
    }
    return m;
    
}

void InsertDatabase(MYSQL *m)
{
    if (NULL == m)
    {
        return;
    }
    
    int ret = mysql_query(m,"set names utf8");
    if (ret != 0)
    {
        cout<<mysql_error(m)<<endl;
        return;
    }
    char sql[128] = {0};
    int id,age;
    char name[32] = {0},birth[32] = {0},sex[12] = {0},tel[12] = {0};
    cout<<"input:id,name,birth,age,sex,tel:"<<endl;
    cin>>id>>name>>birth>>age>>sex>>tel;
    sprintf(sql,"insert into stu (id,name,birth,age,sex,tel) values(%d,'%s','%s',%d,'%s','%s')",
    id,name,birth,age,sex,tel);
    ret = mysql_query(m,sql);
    if(ret != 0)
    {
        cout<< mysql_error(m)<<endl; //打印错误信息
        return;
    }
    cout<<"插入成功"<<endl;
}

void FindDataBase(MYSQL *m)
{
    if(m == NULL)
    {
        return;
    }
        int ret = mysql_query(m,"set names utf8");
    if(ret != 0)
    {
        cout<< mysql_error(m)<<endl; //打印错误信息
        return;
    }
    ret = mysql_query(m,"select * from stu;");
    if(ret != 0)
    {
        cout<< mysql_error(m)<<endl; //打印错误信息
        return;
    }
    MYSQL_RES * res = mysql_store_result(m); //获取查询到的结果
    if(NULL == res)
    {
        cout<< mysql_error(m)<<endl; //打印错误信息
        return;
    }
    //获取字段数
    int field = mysql_num_fields(res);
    MYSQL_FIELD *f; //结构体
    while(f = mysql_fetch_field(res)) //Get the specific field name
    {
        cout<<setw(20)<<setiosflags(ios::left)<<f->name; //打印字段名
    }
    cout<<endl;
    //获取每一条记录
    MYSQL_ROW r; //数组
    while(r = mysql_fetch_row(res))
    {
        for(int i = 0 ; i < field;i++)
        {
            cout<<setw(20)<<setiosflags(ios::left)<<r[i];
        }
        cout<<endl;
    }
}

int main(int argc, char const *argv[])
{
    MYSQL *mysql; //创建mysql变量
    mysql = Init();
    if(mysql != NULL)
    {
        cout<<"链接数据库成功"<<endl;
    }
    else
    {
        cout<<"初始化数据库失败"<<endl;
    }
    //插入数据
    InsertDatabase(mysql);
    FindDataBase(mysql);
    return 0;
}