postgreSQL獲得指定表的列數

//g++ getTableFieldNum.cpp pqCopy.cpp -I /usr/local/pgsql/include/ -L/usr/local/pgsql/lib -lpq -o get -g
#include <libpq-fe.h>
#include <iostream>
#include "pqCopy.h"

 

using namespace std;

char pDBServer[STR_LEN+1];
char g_strDBName[STR_LEN +1];
char pDBUser[STR_LEN+1];
char pDBPwd[STR_LEN+1];
int g_nClientEncoding;

bool getTableColumn(char *par_strTableName, int &par_usColumnNO)
{
 PGconn* pDBconn = NULL;
 pDBconn = connectDB();
 int status = -1;

 PGresult *res = NULL;
 char pSQL[STR_LEN +1] = {0};
 snprintf(pSQL,STR_LEN,"select * from td_usergrp_waphost_d_20120416 limit 1;");

 res = PQexec(pDBconn, "BEGIN");

 if(PQresultStatus(res) != PGRES_COMMAND_OK) //成功完成一個不返回數據的命令
 {
  //LOG("執行BEGIN失敗[%s]", PQerrorMessage(PGconn));
 }

 PQclear(res);
 
 res = PQexec(pDBconn, pSQL);

 status = PQresultStatus(res);

 if (status != PGRES_TUPLES_OK) //成功執行一個返回數據的查詢查詢
 {
  LOG("查詢表失敗");
  char *pStrError = PQerrorMessage(pDBconn);
  printf("sql: %s\n", pStrError);

  PQclear(res);
 }

 par_usColumnNO =  PQnfields(res);
 cout << PQnfields(res) << endl;
 PQclear(res);

 res = PQexec(pDBconn, "END");
 PQclear(res);

}

int main()
{
 strncpy( pDBServer, "192.168.227.128", STR_LEN );
 strncpy(g_strDBName, "test", STR_LEN);
 strncpy(pDBUser, "postgres", STR_LEN);
 strncpy(pDBPwd, "123456", STR_LEN);
 char strTable[100];
 int usColumnNO = 0;
 getTableColumn(strTable, usColumnNO);

 cout << usColumnNO << endl;
}