libpqxx で レコードを一行ずつ表示する

一行ずつカンマ区切りで表示する

ソースコード

#include "ClibpqxxMap.h"
#include <iostream>
#include <pqxx/pqxx>
using namespace std;
using namespace pqxx;

int main()
{
 try {
 connection Conn("dbname=postgres user=postgres");
 work T(Conn);
 result r(T.exec("select * from test"));

//一行ずつ表示する
const int num_rows = r.size();
 for (int rownum = 0; rownum < num_rows; ++rownum)
 {
 std::cout << "r.size" << std::endl;
 const pqxx::row row = r[rownum];
 const int num_cols = row.size();
 for (int colnum = 0; colnum < num_cols; ++colnum)
 {
 const pqxx::field field = row[colnum];
 string fieldStr = field.c_str();
 if (colnum +1 < num_cols) {
 fieldStr = fieldStr + ",";
 }
std::cout << fieldStr ;
}
std::cout << std::endl;
 }
 //T.commit();
 Conn.disconnect();
 }
 catch (const exception &e) {
 cerr << e.what() << endl;
 return 1;
 }
 return 0;
}

実行結果

さらに改良し、１カラムずつ出力

ソースコード

#include "ClibpqxxMap.h"
#include <iostream>
#include <pqxx/pqxx>
using namespace std;
using namespace pqxx;

/*
自作split
*/
std::vector<std::string> split(const std::string input, char delimiter)
{
 std::istringstream stream(input);

 std::string field;
 std::vector<std::string> result;
 while (std::getline(stream, field, delimiter)) {
 result.push_back(field);
 }
 return result;
}

int main()
{
try {
 connection Conn("dbname=postgres user=postgres");
 work T(Conn);
 result r(T.exec("select * from test"));
const int num_rows = r.size();
for (int rownum = 0; rownum < num_rows; ++rownum)
 {
 const pqxx::row row = r[rownum];
 const int num_cols = row.size();
 string record = "";
for (int colnum = 0; colnum < num_cols; ++colnum)
 {
 const pqxx::field field = row[colnum];
 string fieldStr = field.c_str();
//次も値があるかチェック
 int chCnt = colnum;
 record = record + fieldStr;
 if (chCnt +1 < num_cols) {
 record = record + ",";
 }
 }
 cout << endl;
std::cout << "record : " << record << endl;
// カンマで区切る
 cout << "---split----" << endl;
 for (const string& s : split(record, ',')) {
 cout << s << endl;
 }
 }
 cout << endl;

 //T.commit();
 Conn.disconnect();
 }

 catch (const exception &e) {
 cerr << e.what() << endl;
 return 1;
 }
 return 0;
}

実行結果