MySQL C庫的使用

1.初始化和清理

MYSQL mysql;            //數(shù)據(jù)庫句柄
MYSQL_RES* res;         //查詢結(jié)果集
MYSQL_ROW row;          //記錄結(jié)構(gòu)體(就是一行數(shù)據(jù))
mysql_init(&mysql);      //初始化數(shù)據(jù)庫(單線程模式mysql_init自動調(diào)用匣吊，線程不安全)
mysql_options(&mysql, MYSQL_SET_CHARSET_NAME, "gbk");  //設(shè)置字符編碼
int ret = mysql_options(&mysql, MYSQL_OPT_CONNECT_TIMEOUT, &to); //超時設(shè)置暑椰，失敗返回非0 
int reconn = 1;                                                  
ret = mysql_options(&mysql, MYSQL_OPT_RECONNECT, &reconn);   //設(shè)置自動重連
mysql_free_result(res);     //關(guān)閉結(jié)果集
mysql_close(&mysql);        //關(guān)閉數(shù)據(jù)庫連接
mysql_library_end();

2.連接與查詢數(shù)據(jù)庫

mysql_real_connect(&mysql,"127.0.0.1","root","root123456","hui",3306,NULL,0) //失敗返回NULL
const char* sql = "select * from students";         //sql語句
ret = mysql_real_query(&mysql, sql,strlen(sql));    //查詢
res = mysql_store_result(&mysql);                   //獲取查詢結(jié)果集
int field_num = mysql_num_fields(res);              //獲取表字段的數(shù)量
MYSQL_FIELD* fields = mysql_fetch_fields(res);      //獲取表字段名數(shù)組
MYSQL_ROW row = mysql_fetch_row(res)侄刽；               //從結(jié)果集中獲取一行數(shù)據(jù)
unsigned long* len_ptr = mysql_fetch_lengths(res);//從結(jié)果集中獲取一行字段數(shù)據(jù)的長度數(shù)組

sample

#include <mysql.h>
#include <iostream>
#include <stdio.h>
int main()
{
    MYSQL mysql;            //數(shù)據(jù)庫句柄
    MYSQL_RES* res;         //查詢結(jié)果集
    MYSQL_ROW row;          //記錄結(jié)構(gòu)體(就是一行數(shù)據(jù))

    mysql_init(&mysql);      //初始化數(shù)據(jù)庫(單線程模式mysql_init自動調(diào)用泉孩，線程不安全)

    /// <summary>
    /// mysql_options設(shè)置請在連接前設(shè)置
    /// </summary>
    mysql_options(&mysql, MYSQL_SET_CHARSET_NAME, "gbk");  //設(shè)置字符編碼
    int to = 3;

    int ret = mysql_options(&mysql, MYSQL_OPT_CONNECT_TIMEOUT, &to); //超時設(shè)置，失敗返回非0 
    if (ret != int(0))
    {
        std::cout << "設(shè)置超時失敗" << std::endl;
    }

    int reconn = 1;                                                  
    ret = mysql_options(&mysql, MYSQL_OPT_RECONNECT, &reconn);   //設(shè)置自動重連
    if (ret != 0)
    {
        std::cout << "自動重連設(shè)置失敗" << std::endl;
    }
     /// <summary>  
    ///連接數(shù)據(jù)庫
    /// </summary>
    if (mysql_real_connect(&mysql,"127.0.0.1","root","root123456","hui",3306,NULL,0)==NULL)
    {
        printf("錯誤原因：%s\n", mysql_error(&mysql));
        printf("連接失敗");
        exit(-1);
    }

    /// <summary>
    /// 查詢數(shù)據(jù)萧芙；獲取結(jié)果集
    /// </summary>
    const char* sql = "select * from students";
    ret = mysql_real_query(&mysql, sql,strlen(sql));
    if (ret!= 0)
    {
        printf("ret:%s\n", mysql_error(&mysql));
    }
    res = mysql_store_result(&mysql);   
        
    //獲取表字段的數(shù)量
    int field_num = mysql_num_fields(res);
    std::cout << "數(shù)據(jù)庫表字段有" << field_num << "個" << std::endl;

    MYSQL_FIELD* fields = mysql_fetch_fields(res); //獲取表字段名數(shù)組
    for (int i = 0; i < field_num; i++)
    {
        printf("Field %u is %s\n", i, fields[i].name);
    }
    while (row = mysql_fetch_row(res))                               
    {
        unsigned long* len_ptr = mysql_fetch_lengths(res);                 //獲取結(jié)果集的長度要在mysql_fetch_row后
        for (int i = 0;i<field_num;++i)
        {
            printf("字段%d的長度為:%d,字段名為:%s,數(shù)據(jù)為:%s\n",i, len_ptr[i], fields[i].name ,row[i]);
        }
    }
    /// <summary>
    ///釋放結(jié)果集给梅；關(guān)閉數(shù)據(jù)庫
    /// </summary>
    mysql_free_result(res);               
    mysql_close(&mysql);       
    mysql_library_end();
    system("pause");
    return 0;
}