mysl API c 笔记1

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

int mian(int argc,char*argv[]){
    MYSQL mysql;
    char *query="UPDATE book SET title=UPPER(title)";

    mysql_init(&mysql);

    /*connect to server*/
    if(!mysql_real_connect(&mysql,"localhost","root","1qaz2wsx","test",0,NULL,0)){
        fprintf(stderr,"Failed to connect to database.Error :%s\n",mysql_error(&mysql));
        exit(1);
    }

/*mysql_affect_rows 返回最后一次查询所影响的行数*/
    /*update some rows*/
    if(mysql_query(&mysql,query)){
        fprintf(stderr,"Query failed:%s\n",mysql_error(&mysql));
    }
    else {
        printf("%d titles changed.",mysql_affect_rows(&mysql));
    }



    /*mysql_change_user更改登录用户和数据库*/
    /*keep connection ,but remove association to user*/
    if(mysql_change_user(&mysql,"adustdu","1qaz2wsx","TEST1")){
        fprintf(stderr,"Failed to chnage user .Error :%s\n",mysql_error(&mysql));
    }
    /*mysql_character_set_name返回指定连接的默认字符集的名称*/
    /*这里没有给出该函数的具体用法*/
    /*close connection*/
    mysql_close(&mysql);
}

#include<stdio.h>
#include <mysql/mysql.h>
/*mysql_change_user更改登录用户和数据库*/
int main(){
    /*mysql_data_seek跳转到指定行，匹配和mysql_store_result使用，获得该行内容*/
    MYSQL mysql;
    MYSQL_RES* result;
    MYSQL_ROW row;
    char *query="SELECT State FROM tax ORDER BY State";
    mysql_init(&mysql);
    mysql_real_connect(&mysql,"lcoalhost","adustdu","1qaz2wsx","TEST1");

    /*mysql_errno生成错误编码,用作调试*/
    if(mysql_query(&mysql,query)){
        fprintf(stderr,"Query failed :(%d)%s\n",mysql_errno(&mysql),mysql_error(&mysql));
    }
    else {
        /*get result in buffer */
        result =mysql_store_result(&mysql);
        /*Jump to 15th row*/
        mysql_data_seek(result,14);
        /*get row*/
        row=mysql_fetch_row(result);
        /*print state name*/
        printf("%s\n",row[0]);


        /*free result*/
        mysql_free_result(result);
        mysql_close(&mysql);

    }
}

#include <stdio.h>
#include <mysql/mysql.h>
/*mysql_fetch_field提取结果集中有关列的信息，一次一列*/
int mian(int argc,char*argv[]){
    MYSQL mysql;
    MYSQL_RED*result;
    MYSQL_FIELD*field;
    mysql_init(&mysql);

    /*connect to server*/
    if(!mysql_real_connect(&mysql,"localhost","root","1qaz2wsx","test",0,NULL,0)){
        fprintf(stderr,"Failed to connect to database.Error :%s\n",mysql_error(&mysql));
        exit(1);
    }
    mysql_query(&mysql,"SELECT * FROM tax");
    result=mysql_use_result(&mysql);
    /*get information about fields*/
    while((field=mysql_fetch_field(result))){
        printf("Name:%s\n",field->name);
        printf("Table:%s\n",field->table);
        printf("Default value:%s\n\n",field->def);
    }
    /*close connection*/
    mysql_close(&mysql);
}

if(mysql_query(&mysql,"SELECT User ,Host FROM user ORDER BY 1,2"))
    //ORDER BY 1,2意思是先按第一列排序.如果第一列相同的,按第二列降序排序..