c语言怎么调用数据库

在C语言中调用数据库，通常需要使用数据库提供的API或者驱动程序，不同的数据库系统有不同的API和驱动程序，例如MySQL、Oracle、SQL Server等，下面以MySQL为例，介绍如何在C语言中调用数据库。

1、安装MySQL数据库

首先需要在计算机上安装MySQL数据库，可以从官网下载并安装：https://dev.mysql.com/downloads/mysql/

2、安装MySQL C API

MySQL提供了C API，用于在C语言中操作数据库，从MySQL官网下载并安装MySQL Connector/C：https://dev.mysql.com/downloads/connector/c/

3、编写C语言代码

以下是一个简单的C语言程序，用于连接MySQL数据库并执行查询操作：

#include <stdio.h>
#include <stdlib.h>
#include <mysql.h>
int main() {
    MYSQL *conn;
    MYSQL_RES *res;
    MYSQL_ROW row;
    // 初始化MySQL库
    mysql_library_init(0, NULL, NULL);
    // 创建连接句柄
    conn = mysql_init(NULL);
    if (conn == NULL) {
        fprintf(stderr, "Error: %s
", mysql_error(conn));
        exit(1);
    }
    // 连接到MySQL服务器
    if (mysql_real_connect(conn, "localhost", "root", "password", "test", 0, NULL, 0) == NULL) {
        fprintf(stderr, "Error: %s
", mysql_error(conn));
        mysql_close(conn);
        exit(1);
    }
    // 执行查询操作
    if (mysql_query(conn, "SELECT * FROM test_table")) {
        fprintf(stderr, "Error: %s
", mysql_error(conn));
        mysql_close(conn);
        exit(1);
    }
    // 获取查询结果集
    res = mysql_use_result(conn);
    if (res == NULL) {
        fprintf(stderr, "Error: %s
", mysql_error(conn));
        mysql_close(conn);
        exit(1);
    }
    // 遍历查询结果集并打印数据
    while ((row = mysql_fetch_row(res)) != NULL) {
        printf("%st%st%s
", row[0], row[1], row[2]);
    }
    // 释放结果集资源并关闭连接句柄
    mysql_free_result(res);
    mysql_close(conn);
    exit(0);
}

4、编译并运行程序

使用以下命令编译并运行程序：

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