MYSQL的CRUD语句（含c++代码）

一.MySQl表的创建与删除

创建语句与删除语句

注意：

主键的数据类型，不可以是变长度类型需要()限制长度，表名字需要使用``符号来包围。

二.MySQl数据插入

三.MySQl数据删除

四.MySQl数据更新

使用语句

复制代码

SET SQL_SAFE_UPDATES = 0;
show variables like 'SQL_SAFE_UPDATES';

当要哦

第一次修改后:

第二次修改后：

注意：WHERE里面可以使用AND以外，还可以使用OR，来合并多个条件，形成一个更为复杂的条件。

五 .MYSQL数据查询

附录：代码

cpp 复制代码

#include <iostream>
#include <mysql.h>


void show_result(MYSQL_RES* result) {

    //获取结果集列的数量
    unsigned nFiles = mysql_num_fields(result);

    //获取结果集行的数量
    my_ulonglong nRows = mysql_num_rows(result);

    //获取每一列的定义接口：
    MYSQL_FIELD* fields = mysql_fetch_fields(result);

    for (unsigned i = 0; i < nRows; i++) {  //遍历每一行
        MYSQL_ROW row = mysql_fetch_row(result);
        //获取每一行结果
        if (row != NULL) {
            for (unsigned j = 0; j < nFiles; j++) {
                //对于每一行遍历每列的信息
                std::cout << "type:" << fields[j].type << " " << fields[j].name << " : " << row[j] << std::endl;  //对应存储数据的值
            }
        }
        std::cout << "==================" << std::endl;
    }



}

int creat_user(MYSQL* pDB){   //创建新用户
    std::string sql = "CREATE USER 'fc'@'localhost' IDENTIFIED BY ''";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }
    return 0;
}


int grant_userpower(MYSQL* pDB) {  //授予用户权限

    std::string sql = "GRANT ALL PRIVILEGES ON *.* TO 'fc'@'localhost' with grant option";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;
}


int creat_database(MYSQL* pDB) {  //创建数据仓库

    std::string sql = "CREATE DATABASE hello";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;
}


int use_database(MYSQL* pDB) {  //选择数据仓库
    std::string sql = "use hello;";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;
}


int grant_database_power(MYSQL* pDB) {  //授予仓库权限

    std::string sql = "GRANT ALL ON hello.* TO 'fc'@'localhost'";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;
}


int create_table(MYSQL* pDB) {   //创建数据库的表

    std::string sql = "CREATE TABLE IF NOT EXISTS `hello` (`num` char(16) PRIMARY KEY)engine=InnoDB default charset=UTF8MB4;";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;

}


int insert_data(MYSQL* pDB) {   //插入数据库数据

    std::string sql = "insert into `hello` (`编号`) values (\"9527\");";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }
    
    return 0;

}

int delete_data(MYSQL* pDB) {  //删除所筛选的数据

    std::string sql = "delete from `hello` where `编号`=\"9527\";";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;
}

int up_data(MYSQL* pDB) {  //修改所筛选的数据

    std::string sql = "update `hello` set age=30 where `编号`=\"9527\";";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    return 0;
}

int make_query(MYSQL* pDB) {  //查询数据库中的数值

    std::string sql = "select * from `hello`;";
    int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());

    if (ret != 0) {
        std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
        return -1;
    }

    MYSQL_RES* result = mysql_store_result(pDB);
    if (result != NULL) {
        show_result(result);    //展示数据
        mysql_free_result(result);   //释放结果,与use_result相互对应
    }

    return 0;
}





int fe() {

    setlocale(LC_ALL, "en_GB.UTF-8"); //设置控制台编码
    MYSQL* mysql = new MYSQL();
    MYSQL* pDB = mysql_init(mysql);  //初始化mysql对象

    //这里两个变量 mysql和pDB 两个变量记录（指向）同一个值避免初始化失败后返回NULL指针内存泄漏的风险
    if (pDB == NULL) {
        std::cout << "mysql_init failed!" << std::endl;
        return -1;
    }

    pDB = mysql_real_connect(pDB, "localhost", "root", "1234", "mysql", 3306, NULL, 0);

    //连接数据库
    std::cout << pDB << std::endl;
    if (pDB) {
        //creat_user(pDB);
        //grant_userpower(pDB);
        //creat_database(pDB);
        //grant_database_power(pDB);

        //获取SQL的数据
        //use_database(pDB);
       
        //make_query(pDB);

    }

    mysql_close(pDB);

    delete(mysql);

    return 0;

}

int main()
{
    fe();
    return 0;
   
}