c/c++连接postgresql之后的基本使用函数

一、测试是否连接成功

#include "stdafx.h"
#include <stdio.h>  
#include <stdlib.h>  
#include <libpq-fe.h>  
 
void do_exit(PGconn *conn) {  
 
    PQfinish(conn);  
    exit(1);  
}  
 
int main() {  
 
    PGconn *conn = PQconnectdb("user=postgres password=123 dbname=postgres");  
 
    if (PQstatus(conn) == CONNECTION_BAD) {  
 
        fprintf(stderr, "Connection to database failed: %s\n",  
            PQerrorMessage(conn));  
        do_exit(conn);  
    }  
 
    char *user = PQuser(conn);  
    char *db_name = PQdb(conn);  
    char *pswd = PQpass(conn);  
 
    printf("User: %s\n", user);  
    printf("Database name: %s\n", db_name);  
    printf("Password: %s\n", pswd);  
 
    PQfinish(conn);  
 
    return 0;  
}  

二、通过c向数据库添加表及数据

#include <stdio.h>  
#include <stdlib.h>  
#include <libpq-fe.h>  
 
void do_exit(PGconn *conn, PGresult *res) {  
 
    fprintf(stderr, "%s\n", PQerrorMessage(conn));      
 
    PQclear(res);  
    PQfinish(conn);      
 
    exit(1);  
}  
 
int main() {  
 
    PGconn *conn = PQconnectdb("user=postgres password=123 dbname=postgres");  
 
    if (PQstatus(conn) == CONNECTION_BAD) {  
 
        fprintf(stderr, "Connection to database failed: %s\n",  
            PQerrorMessage(conn));  
 
        PQfinish(conn);  
        exit(1);  
    }  
 
    PGresult *res = PQexec(conn, "DROP TABLE IF EXISTS Cars");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);  
    }  
 
    PQclear(res);  
 
    res = PQexec(conn, "CREATE TABLE Cars(Id INTEGER PRIMARY KEY," \  
        "Name VARCHAR(20), Price INT)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);   
    }  
 
    PQclear(res);  
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(1,'Audi',52642)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK)   
        do_exit(conn, res);       
 
    PQclear(res);      
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(2,'Mercedes',57127)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);      
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(3,'Skoda',9000)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);    
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(4,'Volvo',29000)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);        
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(5,'Bentley',350000)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);    
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(6,'Citroen',21000)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);    
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(7,'Hummer',41400)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);    
 
    res = PQexec(conn, "INSERT INTO Cars VALUES(8,'Volkswagen',21600)");  
 
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {  
        do_exit(conn, res);     
    }  
 
    PQclear(res);    
    PQfinish(conn);  
 
    return 0;  
}  

三、读取数据库中数据

#include <stdio.h>  
#include <stdlib.h>  
#include <libpq-fe.h>  
 
void do_exit(PGconn *conn) {  
 
    PQfinish(conn);  
    exit(1);  
}  
 
int main() {  
 
    PGconn *conn = PQconnectdb("user=postgres password=123 dbname=postgres");  
 
    if (PQstatus(conn) == CONNECTION_BAD) {  
 
        fprintf(stderr, "Connection to database failed: %s\n",  
            PQerrorMessage(conn));  
        do_exit(conn);  
    }  
 
    PGresult *res = PQexec(conn, "SELECT * FROM Cars LIMIT 5");      
 
    if (PQresultStatus(res) != PGRES_TUPLES_OK) {  
 
        printf("No data retrieved\n");          
        PQclear(res);  
        do_exit(conn);  
    }      
 
    int rows = PQntuples(res);  
 
    for(int i=0; i<rows; i++) {  
 
        printf("%s %s %s\n", PQgetvalue(res, i, 0),   
            PQgetvalue(res, i, 1), PQgetvalue(res, i, 2));  
    }      
 
    PQclear(res);  
    PQfinish(conn);  
 
    return 0;  
}  

转载自：https://blog.csdn.net/zsc201825/article/details/83379100