MySql 100104：Connector/C

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1．框架

基本步骤：

a) mysql_library_init()

b)mysql_init()

c) Issue SQL statements and process their results

d) mysql_close()

e) mysql_library_end()

 

The client can send SQL statement to the server using mysql_query() or mysql_real_query() The diff is that mysql_query() expects the query to be specified as a null-terminated string whereas mysql_real_query() expects a counted string.  If the string contains binary data(which may include null bytes), you must use mysql_real_query().

For SELECT queries, mysql_store_result() get all the row returned from the server and stores them in the client. And mysql_use_result() initiates a row-by-row result set, but does not actually get any rows from the server.   In both cases, you access rows by calling mysql_fetch_row().

After you are done with a result set, call mysql_free_result() to free the memory used for it.

 

if using mysql_store_result, you can move back and forth in the result set by using mysql_data_seek() or mysql_row_seek(), and you can also find out how many rows there are by calling mysql_num_rows().

 

2．主要函数

 

id	func	Description
1	mysql_library_init()	初始化mysql library. 对于mysql单线程场景，可以忽略，mysql_init()默认会调用这个函数。对于多线程场景，应当在起始时调用。
2	mysql_library_end()	对应mysql_library_end()，建议调用。
3	mysql_init()	初始化MYSQL结构，
4	mysql_real_connect()	给定host, user, passwd, port，dbname等，连接mysql server。注意不应当再使用过期的mysql_connect()
5	mysql_close()	关闭连接。
6	mysql_store_result()	查询结果集合全部取回client
7	mysql_use_result()	一行一行的取回查询结果集合
8	mysql_free_result()	释放结果集合占用的内存
9	mysql_fetch_row()	取结果集合中的下一行
10	mysql_errno()	错误码
11	mysql_error()	错误信息

 

3．例子

预备条件：

server上的账户 root:passwd@localhost:3306, 数据库是world, 其中的表city结构如下

 

mysql> desc city;

+-------------+----------+------+-----+---------+----------------+

| Field       | Type     | Null | Key | Default | Extra          |

+-------------+----------+------+-----+---------+----------------+

| ID          | int(11)  | NO   | PRI | NULL    | auto_increment |

| Name        | char(35) | NO   |     |         |                |

| CountryCode | char(3)  | NO   |     |         |                |

| District    | char(20) | NO   |     |         |                |

| Population  | int(11)  | NO   |     | 0       |                |

+-------------+----------+------+-----+---------+----------------+

5 rows in set (0.00 sec)

 

 

程序如下

 

// mysqlTest.cpp : 定义控制台应用程序的入口点。

//

 

#include "stdafx.h"

#include "mysql.h"

 

 

#define MYSQL_PORT 3306

#define MYSQL_HOST "localhost"

#define MYSQL_USER "root"

#define MYSQL_PASSWD   "passwd"

#define MYSQL_DB   "world"

 

#define MYSQL_SELECTSTATEMENT    "select id, name, countrycode from city"

 

 

MYSQL mySQLHandler;

 

int _tmain(int argc, _TCHAR* argv[])

{

 

     unsigned int r;

     MYSQL_RES *mySQLRes;

     MYSQL_ROW mySQLRow;

    

     mysql_library_init(0,NULL,NULL);

 

     mysql_init(&mySQLHandler);

 

     printf("1. inited ---------------\n");

 

     if (!mysql_real_connect(&mySQLHandler, MYSQL_HOST, MYSQL_USER, MYSQL_PASSWD, MYSQL_DB,MYSQL_PORT, NULL, 0))

     {

         printf( "Error connecting to database: %s\n",mysql_error(&mySQLHandler));

         return 1;

     }

 

     printf("2. connected ---------------\n");

 

     r = mysql_real_query(&mySQLHandler, MYSQL_SELECTSTATEMENT, (unsigned long) strlen(MYSQL_SELECTSTATEMENT));

 

     if(r)   

     {

         printf( "query err: %s\n",mysql_error(&mySQLHandler));

         return 1;

     }

 

     printf("3.queried ---------------\n");

 

     mySQLRes = mysql_store_result(&mySQLHandler);

 

     if (!mySQLRes)    

     {

         printf( "store result err: %s\n",mysql_error(&mySQLHandler));

         return 1;

     }

 

     printf("3.stored result ---------------\n");

 

     while(mySQLRow = mysql_fetch_row(mySQLRes))

     {

         for(r=0;r

         {

              printf("%s ",mySQLRow[r]);

         }

         printf("\n");

     }

 

     printf("4.fetched rows ---------------\n");

     mysql_free_result(mySQLRes);

 

     printf("5.free result ---------------\n");

 

     mysql_close(&mySQLHandler);

     printf("6.close mysql ---------------\n");

 

//   mysql_library_end();

 

     return 0;

}

 

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