验证

cpp 复制代码

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

int main()
{
    std::cout<<"mysql cilent version: "<<mysql_get_client_info()<<std::endl;
    return 0;
}

注意：使用mysqlclient库需要指明库的位置-L和库的名称-l

shell 复制代码

[wmh@pDaD Test]$ g++ test.cc -o  test -L/lib64/mysql -lmysqlclient
[wmh@pDaD Test]$ ./test
mysql cilent version: 5.7.42

使用

MySQL-5.7API接口介绍

cpp 复制代码

#include <iostream>
#include <mysql/mysql.h>
#include <string>
#include <unistd.h>
const std::string host="127.0.0.1";
const std::string user = "connection";
const std::string passwd="123456";
const std::string db="scott";
const unsigned int port = 3306;
int main()
{
    MYSQL* mysql = mysql_init(nullptr);//初始化MySQL句柄
    if(nullptr == mysql)
    {
        std::cerr<<"init MySQL error"<<std::endl;
        return 1;
    }
    if(mysql_real_connect(mysql,host.c_str(),user.c_str(),passwd.c_str(),db.c_str(),port,nullptr,0) == nullptr)//连接MySQL数据库
    {
        std::cerr<<"connect MySQL error"<<std::endl;
        return 2;
    }
    mysql_set_character_set(mysql,"utf8");//设置字符集编码

    std::string sql="update user set age='60' where id=3";
    
    int n = mysql_query(mysql,sql.c_str());//下发命令
    if(n==0) std::cout<<sql<<"success"<<std::endl;
    else std::cout<<sql<<"failed"<<std::endl;

    mysql_close(mysql);
    return 0;
}

sql 复制代码

mysql> select* from user;
+----+-----+-----------+
| id | age | name      |
+----+-----+-----------+
|  1 |  28 | 赵志敬    |
|  3 |  18 | 杨过      |
|  4 |  16 | 小龙女    |
+----+-----+-----------+

mysql> select* from user;
+----+-----+-----------+
| id | age | name      |
+----+-----+-----------+
|  1 |  28 | 赵志敬    |
|  3 |  60 | 杨过      |
|  4 |  16 | 小龙女    |
+----+-----+-----------+

select特殊点

sql执行完以后，如果是查询语句，我们要能看到数据显示出来，那么就需要mysql_store_result这个函数来保存结果到本地

cpp 复制代码

MYSQL_RES *mysql_store_result(MYSQL *mysql);

获取结果行数mysql_num_rows

cpp 复制代码

my_ulonglong mysql_num_rows(MYSQL_RES *res);

获取结果列数mysql_num_fields

cpp 复制代码

unsigned int mysql_num_fields(MYSQL_RES *res);

以列为单位获取列属性mysql_fetch_fields

cpp 复制代码

MYSQL_FIELD *mysql_fetch_fields(MYSQL_RES *res);

cpp 复制代码

typedef struct st_mysql_field {
  char *name;                 /* Name of column */
  char *org_name;             /* Original column name, if an alias */
  char *table;                /* Table of column if column was a field */
  char *org_table;            /* Org table name, if table was an alias */
  char *db;                   /* Database for table */
  char *catalog;	      /* Catalog for table */
  char *def;                  /* Default value (set by mysql_list_fields) */
  unsigned long length;       /* Width of column (create length) */
  unsigned long max_length;   /* Max width for selected set */
  unsigned int name_length;
  unsigned int org_name_length;
  unsigned int table_length;
  unsigned int org_table_length;
  unsigned int db_length;
  unsigned int catalog_length;
  unsigned int def_length;
  unsigned int flags;         /* Div flags */
  unsigned int decimals;      /* Number of decimals in field */
  unsigned int charsetnr;     /* Character set */
  enum enum_field_types type; /* Type of field. See mysql_com.h for types */
  void *extension;
} MYSQL_FIELD;

以行为单位获取结果内容mysql_fetch_row

cpp 复制代码

MYSQL_ROW mysql_fetch_row(MYSQL_RES *result);

MYSQL_ROW其实就是char **.当成一个二维数组

释放结果集内存

cpp 复制代码

void mysql_free_result(MYSQL_RES *result)

调用mysql_store_result返回结构体，这个函数malloc了一片内存空间来存储查询过来的数据，需要free掉

整体示例

cpp 复制代码

#include <iostream>
#include <mysql/mysql.h>
#include <string>
#include <unistd.h>
const std::string host = "127.0.0.1";
const std::string user = "connection";
const std::string passwd = "123456";
const std::string db = "scott";
const unsigned int port = 3306;
int main()
{
    MYSQL *mysql = mysql_init(nullptr); // 初始化MySQL句柄
    if (nullptr == mysql)
    {
        std::cerr << "init MySQL error" << std::endl;
        return 1;
    }
    if (mysql_real_connect(mysql, host.c_str(), user.c_str(), passwd.c_str(), db.c_str(), port, nullptr, 0) == nullptr) // 连接MySQL数据库
    {
        std::cerr << "connect MySQL error" << std::endl;
        return 2;
    }
    mysql_set_character_set(mysql, "utf8"); // 设置字符集编码

    // std::string sql="update user set age='60' where id=3";
    std::string sql = "select * from user";
    int n = mysql_query(mysql, sql.c_str()); // 下发命令
    if (n == 0)
        std::cout << sql << "success" << std::endl;
    else
        std::cout << sql << "failed" << std::endl;

    // 保存结果集转储到res中
    MYSQL_RES *res = mysql_store_result(mysql);
    if (res == nullptr)
    {
        std::cerr << "mysql_store_result_error" << std::endl;
    }
    int rows = mysql_num_rows(res);     // 获取行数
    int fields = mysql_num_fields(res); // 获取列数

    std::cout << "行: " << rows << std::endl;
    std::cout << "列：" << fields << std::endl;

    // 获取列属性
    MYSQL_FIELD *fields_array = mysql_fetch_fields(res);
    for (int i = 0; i < fields; ++i)
    {
        std::cout << fields_array[i].name << "\t"; // 打印列名
    }
    std::cout << std::endl;

    for (int i = 0; i < rows; i++)
    {
        //row可以认为是一个char** 指针
        MYSQL_ROW row = mysql_fetch_row(res);//以行为单位获取记录
        for (int j = 0; j < fields; ++j)
        {
            std::cout << row[j] << "\t";
        }
        std::cout << "\n";
    }
    std::cout << fields_array[0].db << " " << fields_array[0].table << std::endl;
    mysql_free_result(res);//释放结果集

    mysql_close(mysql);//关闭MYSQL句柄

    return 0;
}