在C语言怎样对数据和 *** 作的封装

以下仅为个人理解：

数据封装就是使用类似结构体的形式，将多个相关数据合并到一个结构体中，在程序中作为一个整体进行付值和调用 *** 作。

*** 作封装就是对多个重复使用且具有相同功能的语句进行整合，打包成一个实现固定功能的函数。

1.需要用到mysql c api

2.步骤通常是：连接数据库，执行查询，异常处理这些。

3.你需要对api 进行一些了解，然后合理调用。

参考代码：

//连接代码：

/*

* connect1.c - connect to and disconnect from MySQL server

*/

#include <my_global.h>

#include <my_sys.h>

#include <mysql.h>

static char *opt_host_name = NULL /* server host (default=localhost) */

static char *opt_user_name = NULL /* username (default=login name) */

static char *opt_password = NULL /* password (default=none) */

static unsigned int opt_port_num = 0 /* port number (use built-in value) */

static char *opt_socket_name = NULL /* socket name (use built-in value) */

static char *opt_db_name = NULL /* database name (default=none) */

static unsigned int opt_flags = 0 /* connection flags (none) */

static MYSQL *conn/* pointer to connection handler */

int

main (int argc, char *argv[])

{

/* initialize connection handler */

conn = mysql_init (NULL)

if (conn == NULL)

{

fprintf (stderr, "mysql_init() failed (probably out of memory)\n")

exit (1)

}

/* connect to server */

if (mysql_real_connect (conn, opt_host_name, opt_user_name, opt_password,

opt_db_name, opt_port_num, opt_socket_name, opt_flags) == NULL)

{

fprintf (stderr, "mysql_real_connect() failed\n")

mysql_close (conn)

exit (1)

}

/* disconnect from server */

mysql_close (conn)

exit (0)

}

//处理sql 语句的函数：

void

process_statement (MYSQL *conn, char *stmt_str)

{

MYSQL_RES *res_set

if (mysql_query (conn, stmt_str) != 0) /* the statement failed */

{

print_error (conn, "Could not execute statement")

return

}

/* the statement succeededdetermine whether it returned data */

res_set = mysql_store_result (conn)

if (res_set) /* a result set was returned */

{

/* process rows and then free the result set */

process_result_set (conn, res_set)

mysql_free_result (res_set)

}

else /* no result set was returned */

{

/*

* does the lack of a result set mean that the statement didn't

* return one, or that it should have but an error occurred?

*/

if (mysql_field_count (conn) == 0)

{

/*

* statement generated no result set (it was not a SELECT,

* SHOW, DESCRIBE, etc.)just report rows-affected value.

*/

391

Processing SQL Statements

printf ("%lu rows affected\n",

(unsigned long) mysql_affected_rows (conn))

}

else /* an error occurred */

{

print_error (conn, "Could not retrieve result set")

}

}

}

//以上提供的是常规的处理，你需要根据实际情况完善。

//同时调用了一些mysql 的api函数。

ref:

MySQL

(Fourth Edition)

Paul DuBois

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