linux c]mysql 编程笔记

#include <mysql.h>

相关函数:

MYSQL *mysql_init(MYSQL *);//这里称之为载入函数吧，返回的MYSQL指针要用到后续的函数中int mysql_options(MYSQL *connection, enum option_to_set,const char *argument);//设置MYSQL*的一些属性，比如超时时间等MYSQL *mysql_real_connect(MYSQL *connection,                const char *server_host,                const char *sql_user_name,                const char *sql_password,                const char *db_name,                unsigned int port_number,//置0连接默认端口，一般为3306                const char *unix_socket_name,//NULL                unsigned int flags);//无另外属性时置0//连接函数void mysql_close(MYSQL *connection);//关闭连接unsigned int mysql_errno(MYSQL *connection);//返回错误代码char *mysql_error(MYSQL *connection);//返回错误信息int mysql_query(MYSQL *connection, const char *query);//执行sql语句my_ulonglong mysql_affected_rows(MYSQL *connection);//返回执行语句过后受影响的行数MYSQL_RES *mysql_store_result(MYSQL *connection);//返回执行结果，适用于数据量较小时my_ulonglong mysql_num_rows(MYSQL_RES *result);//返回上面函数返回结果的行数MYSQL_ROW mysql_fetch_row(MYSQL_RES *result);//抽取一条记录，返回NULL时表示抽取完记录或者错误void mysql_data_seek(MYSQL_RES *result, my_ulonglong offset);//调整数据位置，offset为0时，下次调用mysql_fetch_row将返回result第一条记录MYSQL_ROW_OFFSET mysql_row_tell(MYSQL_RES *result);//返回当前的位置MYSQL_ROW_OFFSET mysql_row_seek(MYSQL_RES *result, MYSQL_ROW_OFFSET offset);//移动数据位置，并返回先前的位置，可以和上一个函数结合使用void mysql_free_result(MYSQL_RES *result);//释放result空间MYSQL_RES *mysql_use_result(MYSQL *connection);//返回执行结果，适用于数据量较大时unsigned int mysql_field_count(MYSQL *connection);//返回查询结果中的列数（column数）MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result);//获得查询结果中的列名等信息（表头信息）

例子：

创建测试数据库
mysql> create database test;
创建用户
mysql> grant all on test.* to test@'localhost' identified by 'test';

sql文件：

---- Create the table children--CREATE TABLE children (childno int(11) NOT NULL auto_increment,fname varchar(30),age int(11),PRIMARY KEY (childno));---- Populate the table ‘children’--INSERT INTO children(childno,fname,age) VALUES(1,'Jenny',21);INSERT INTO children(childno,fname,age) VALUES(2,'Andrew',17);INSERT INTO children(childno,fname,age) VALUES(3,'Gavin',8);INSERT INTO children(childno,fname,age) VALUES(4,'Duncan',6);INSERT INTO children(childno,fname,age) VALUES(5,'Emma',4);INSERT INTO children(childno,fname,age) VALUES(6,'Alex',15);INSERT INTO children(childno,fname,age) VALUES(7,'Adrian',9);

导入sql文件：

mysql -u test --password=test test<mysqlchildren.sql

导入后的情况：

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| children |
+----------------+
1 row in set (0.00 sec)

mysql> select * from children;
+---------+--------+------+
| childno | fname | age |
+---------+--------+------+
| 1 | Jenny | 21 |
| 2 | Andrew | 17 |
| 3 | Gavin | 8 |
| 4 | Duncan | 6 |
| 5 | Emma | 4 |
| 6 | Alex | 15 |
| 7 | Adrian | 9 |
+---------+--------+------+
7 rows in set (0.00 sec)

C代码:

#include <stdio.h>#include <stdlib.h>#include <mysql.h>MYSQL *mysql_main;MYSQL_RES *res_ptr;MYSQL_ROW sqlrow;void display_header();void display_row();int main(int argc,char *argv[]){    int res;    int first_row = 1;    mysql_main = mysql_init(NULL);    if(!mysql_main)    {        fprintf(stderr,"mysql_init failed\n");        return EXIT_FAILURE;    }    mysql_main = mysql_real_connect(mysql_main,"localhost","test","test","test",0,NULL,0);    if(mysql_main)    {        printf("Connection success:\n");        res = mysql_query(mysql_main,"SELECT childno,fname,age FROM children WHERE age>5");        if(res)        {            fprintf(stderr,"SELECT error: %s\n",mysql_error(mysql_main));        }        else        {            res_ptr = mysql_use_result(mysql_main);            if(res_ptr)            {                while((sqlrow = mysql_fetch_row(res_ptr)))                {                    if(first_row)                    {                        display_header();                        first_row = 0;                    }                    display_row();                }            }        }    }    else    {        printf("Connection failed\n");    }    mysql_close(mysql_main);    return EXIT_SUCCESS;}void display_header(){    MYSQL_FIELD *field_ptr;    printf("Column details:\n");    while((field_ptr = mysql_fetch_field(res_ptr))!=NULL)    {        printf("\t Name: %s\n",field_ptr->name);        printf("\t Type: ");        if(IS_NUM(field_ptr->type))        {            printf("Numeric filed\n");        }        else        {            switch(field_ptr->type)            {            case FIELD_TYPE_VAR_STRING:                printf("VARCHAR\n");                break;            case FIELD_TYPE_LONG:                printf("LONG\n");                break;            default:                printf("Type is %d,check in mysql_com.h\n",field_ptr->type);            }        }        printf("\t MAX width %ld\n",field_ptr->length);        if(field_ptr->flags&AUTO_INCREMENT_FLAG)            printf("\t Auto increments\n");        printf("\n");    }}void display_row(){    unsigned int field_count;    field_count = 0;    while(field_count<mysql_field_count(mysql_main))    {        if(sqlrow[field_count]) printf("%s ",sqlrow[field_count]);        else printf("NULL");        field_count++;    }    printf("\n");}

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

./test

结果如下：

Connection success:
Column details:
Name: childno
Type: Numeric filed
MAX width 11
Auto increments

Name: fname
Type: VARCHAR
MAX width 30

Name: age
Type: Numeric filed
MAX width 11

1 Jenny 21
2 Andrew 17
3 Gavin 8
4 Duncan 6
6 Alex 15
7 Adrian 9