mysql基础：mysql与C结合实例

一个简单的mysql与C的交互，使用了一些mysql的C API！

老鸟掠过，新手能够看看！

      /******************************************
  本文件学习mysql的database使用
  学习mysql的C接口
  包括初始化db，检查数据库是否存在，不存在就创建。
  检查表是否存在，不存在则创建
 *****************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//须要包括mysql的头文件，/usr/include/mysql/
//编译的时候须要加上-L/usr/lib/ -lmysqlclient -I/usr/include/mysql选项

#include <mysql.h> //主要的头文件，一些重要结构体的声明
#include <errmsg.h>//错误信息的存放
#include <mysql_version.h>  //包括当前mysql的版本号信息
//////////////////所有变量，宏定义//////////////////////
#define DEBUG
#define SERVER_HOST "localhost"  //mysql的远程地址
#define SERVER_USER "root"      //数据库登录名
#define SERVER_PWD  "123"  //数据库登录password

#define DB_NAME     "tmp_db"    //新建数据库的名字
#define TABLE_NAME  "mytables"  //库中的表

int check_tbl(MYSQL* mysql,char *name);
int check_db(MYSQL *mysql,char *db_name);

int init_db()
{

    int err=0;
    MYSQL mysql;

    if(!mysql_init(&mysql)){
        perror("mysql_init:");
        exit(1);
    }   

    if(!mysql_real_connect(&mysql,SERVER_HOST,SERVER_USER,SERVER_PWD,NULL,0,NULL,0))
    {   
        perror("mysql_real_connect");
        exit(1);
    }   
    printf("connected.....\n");

    err = check_db(&mysql,DB_NAME);
    if(err != 0)
    {   
        printf("create db is err!\n");
        mysql_close(&mysql);
        exit(1);
    }   
    //select which db
	    if(mysql_select_db(&mysql,DB_NAME)) //return 0 is success ,!0 is err
    {
        perror("mysql_select_db:");
        mysql_close(&mysql);
        exit(1);
    }
    //chuangjianbiao
    if((err=check_tbl(&mysql,TABLE_NAME))!=0)
    {
        printf("check_tbl is err!\n");
        mysql_close(&mysql);
        exit(1);
    }
    mysql_close(&mysql);
    return 0;
}

int check_db(MYSQL *mysql,char *db_name)
{
    MYSQL_ROW row = NULL;
    MYSQL_RES *res = NULL;

    res = mysql_list_dbs(mysql,NULL);
    if(res)
    {
        while((row = mysql_fetch_row(res))!=NULL)
        {
            printf("db is %s\n",row[0]);
            if(strcmp(row[0],db_name)==0)
            {
                printf("find db %s\n",db_name);
                break;
            }
        }
        //mysql_list_dbs会分配内存，须要使用mysql_free_result释放
        mysql_free_result(res);
    }
    if(!row)  //没有这个数据库，则建立
    {
        char buf[128]={0};
        strcpy(buf,"CREATE DATABASE ");
        strcat(buf,db_name);
#ifdef DEBUG
        printf("%s\n",buf);
#endif
        if(mysql_query(mysql,buf)){
            fprintf(stderr,"Query failed (%s)\n",mysql_error(mysql));
            exit(1);
        }
    }
    return 0;
}

int check_tbl(MYSQL* mysql,char *name)
{
    if(name == NULL)
        return 0;
    MYSQL_ROW row=NULL;
    MYSQL_RES *res = NULL;
    res = mysql_list_tables(mysql,NULL);
    if(res)
    {
        while((row = mysql_fetch_row(res))!=NULL)
        {
            printf("tables is %s\n",row[0]);
            if(strcmp(row[0],name) == 0)
            {
                printf("find the table !\n");
                break;
            }
        }
        mysql_free_result(res);
    }
    if(!row) //create table
    {
        char buf[128]={0};
        char qbuf[128]={0};
        snprintf(buf,sizeof(buf),"%s (name VARCHAR(20),sex char(1),score int(3));",TABLE_NAME);
        strcpy(qbuf,"CREATE TABLE ");
        strcat(qbuf,buf);
//#ifdef DEBUG
        printf("%s\n",qbuf);
//#endif
        if(mysql_query(mysql,qbuf)){
            fprintf(stderr,"Query failed (%s)\n",mysql_error(mysql));
            exit(1);
        }
    }
    return 0;
}

int main()
{
    int err=0;
    err = init_db();

    return 0;
}

    

编译的方法：最后的-I一定要注意检查这个文件夹是不是存在，否则会报错

      gcc -o mysql mysql.c -L/usr/lib/ -lmysqlclient -I/usr/include/mysql
    

报错：

      root@jack-desktop:~# gcc -o mysql mysql.c -L/usr/lib/ -lmysqlclient
gcc: mysql.c: 没有那个文件或文件夹
root@jack-desktop:~# 
root@jack-desktop:~# 
root@jack-desktop:~# cd myc/
root@jack-desktop:myc# gcc -o mysql mysql.c -L/usr/lib/ -lmysqlclient
mysql.c:15:73: error: mysql.h: 没有那个文件或文件夹
mysql.c:16:43: error: errmsg.h: 没有那个文件或文件夹
mysql.c:17:63: error: mysql_version.h: 没有那个文件或文件夹
mysql.c:27: error: expected ‘)’ before ‘*’ token
mysql.c:28: error: expected ‘)’ before ‘*’ token
mysql.c: In function ‘init_db’:
mysql.c:34: error: ‘MYSQL’ undeclared (first use in this function)
mysql.c:34: error: (Each undeclared identifier is reported only once
mysql.c:34: error: for each function it appears in.)
mysql.c:34: error: expected ‘;’ before ‘mysql’
mysql.c:36: error: ‘mysql’ undeclared (first use in this function)
mysql.c: At top level:
mysql.c:73: error: expected ‘)’ before ‘*’ token
mysql.c:109: error: expected ‘)’ before ‘*’ token