通过c ++从sql表中检索数据

Question

标题说我想做以下事情：

我在（在sql中）创建了一个表“辐射”，它是：

现在，我想从c ++能够询问用户“给一个元素”，如果用户给出例如“I”，那么例如检索“halftime”字段。

c ++代码是：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <sys/time.h>
#include <mysql/mysql.h>


using namespace std;

int main()
{ 


MYSQL_RES *result;
MYSQL_ROW row;
MYSQL *connection, mysql;

const char* server="127.0.0.1";
const char* user ="****";
const char* password="****";
const char* database="***";

int state;

mysql_init(&mysql);

connection = mysql_real_connect(&mysql,server,user,password,database,0,0,0);

if (connection == NULL)
    {

cout<<mysql_error(&mysql);

return 1;
    }

state = mysql_query(connection, "SELECT * FROM radiation");

if (state !=0)
    {
    cout <<mysql_error(connection);
   return 1;
    }

result = mysql_store_result(connection);


row=mysql_fetch_row(result);
string name;

cout <<"\nGive the name : "<<endl;
cin >>name;

cout << "\nThe halftime for "<<name << " is "<<**row[2]**->here i want to extract the analogous filed <<" hours";
//}



mysql_free_result(result);

mysql_close(connection);


return 0;
}

我只知道sql的基础知识，我不知道上面做的有多难。

Answer 1

This may help。您只需处理执行查询后得到的结果集。

res = stmt->executeQuery("SELECT * FROM radiation");
while (res->next()) {
  // You can use either numeric offsets...
  cout << "name_id = " << res->getInt(1); // getInt(1)/getString() returns the first column
      }

Answer 2

根据评论中的说明，您只需要正确构建SQL语句：

SELECT halftime FROM RADIATION WHERE name_id = 'Tc'

将结果表示为：

6

更复杂的答案：

std::string column;
std::string name;

// have the user tell you what columns are wanted
cin >> column;

// have the user give you the criteria
cin >> name;

// build the SQL
std::stringstream sql;

sql << "SELECT " << column << " FROM RADIATION WHERE name = '" << name << "'";