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最新推荐文章于 2024-10-15 09:50:30 发布

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本文提供了一段用于连接并查询MySQL数据库的C语言代码示例，详细展示了如何使用MySQL客户端库进行基本的数据库操作，包括连接、执行SQL查询及结果集遍历。

随便传数据库mysql代码上去，仅仅是为了备份而已，SQL命令太多，多翻翻工具书吧，，，，，

now to install MYSQL：

# sudo apt-get install mysql-server mysql-client

(第一次发现图书馆还是you可以用的书嘛，，，)

#include <stdlib.h>
#include <stdio.h>
#include  <mysql/mysql.h>
 MYSQL my_connection;
MYSQL_RES *res_ptr;
MYSQL_ROW sqlrow;
void display_header();
void display_row(MYSQL *ptr);
int main()
{
   	int res;
	int first_row=1;
   	mysql_init(&my_connection);
  	 if (mysql_real_connect(&my_connection, "localhost", "test","test", "testdb", 0, NULL, 0))
   	{
		printf("Connection success\n");
		res = mysql_query(&my_connection, "SELECT childno, fname,  age FROM children WHERE age > 5");
      		if (res)
		{
        		printf("SELECT error: %s\n", mysql_error(&my_connection));
			return -2;
		}
		else
		{
			 res_ptr = mysql_use_result(&my_connection);
			 if (res_ptr)
			{
				display_header();
				while ((sqlrow = mysql_fetch_row(res_ptr)))
				{
   					if(first_row)
					{
						display_header();
						first_row=0;
					}
					display_row(&my_connection);
				}
		     		if (mysql_errno(&my_connection))
				{
				   fprintf(stderr, "Retrive error: s\n",mysql_error(&my_connection));
				   return -3;
		     		}
           		}
          		mysql_free_result(res_ptr);
         	}
         	mysql_close(&my_connection);
		printf("Connection closed.\n");
 	 }
 	else
  	{
    		fprintf(stderr, "Connection failed\n");
   		 if (mysql_errno(&my_connection))
    		{
     			fprintf(stderr, "Connection error %d: %s\n",
      			mysql_errno(&my_connection),mysql_error(&my_connection));
			return -1;
     		}
  	}
  	return 0;
}

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 field \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 %d \n",field_ptr->length);
		if(field_ptr->flags & AUTO_INCREMENT_FLAG)
			printf("\t Auto increments \n");
		printf("\n");
	}
}

void display_row(MYSQL *ptr)
{
	unsigned int field_count;
	field_count=0;
	while(field_count<mysql_field_count(ptr))
	{
		printf("%s ",sqlrow[field_count]);
		field_count++;
	}
	printf("\n");
}