PostgreSQL libpq开发入门

#include <stdio.h>#include <stdlib.h>#include "libpq-fe.h"staticvoidexit_nicely(PGconn*conn) {
PQfinish(conn);
exit(1);
}
intmain(intargc, char**argv) {
constchar*conninfo;
PGconn*conn;
PGresult*res;
intnFields;
inti, j;
if(argc>1)
conninfo=argv[1];
elseconninfo="dbname=postgres user=postgres password=123456 host=localhost";
conn=PQconnectdb(conninfo);
if(PQstatus(conn) !=CONNECTION_OK) {
fprintf(stderr, "%s", PQerrorMessage(conn));
exit_nicely(conn);
    }
res=PQexec(conn, "SELECT pg_catalog.set_config('search_path','',false)");
if(PQresultStatus(res) !=PGRES_TUPLES_OK) {
fprintf(stderr,"SET failed: %s", PQerrorMessage(conn));
PQclear(res);
exit_nicely(conn);
    }
PQclear(res);
res=PQexec(conn, "BEGIN");
if(PQresultStatus(res) !=PGRES_COMMAND_OK) {
fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));
PQclear(res);
exit_nicely(conn);
    }
PQclear(res);
res=PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");
if(PQresultStatus(res) !=PGRES_COMMAND_OK) {
fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
PQclear(res);
exit_nicely(conn);
    }
PQclear(res);
res=PQexec(conn, "FETCH ALL in myportal");
if(PQresultStatus(res) !=PGRES_TUPLES_OK) {
fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));
PQclear(res);
exit_nicely(conn);
    }
nFields=PQnfields(res);
for(i=0; i<nFields; i++)
printf("%-15s", PQfname(res, i));
printf("\n\n");
for(i=0; i<PQntuples(res); i++) {
for(j=0; j<nFields; j++)
printf("%-15s", PQgetvalue(res, i, j));
printf("\n");
    }
PQclear(res);
res=PQexec(conn, "CLOSE myportal");
PQclear(res);
res=PQexec(conn, "END");
PQclear(res);
PQfinish(conn);
return0;
}

cmake_minimum_required(VERSION3.24)
project(pg_testC)
set(CMAKE_C_STANDARD11)
set(INC_DIR/usr/local/pgsql14/include)
set(LINK_DIR/usr/local/pgsql14/lib)
include_directories(${INC_DIR})
link_directories(${LINK_DIR})
add_executable(pg_testtestlibpg.c)
target_link_libraries(pg_testpq)