使用 mysql fetch_object 从多个表中选择数据

Question

我真的是网络应用程序和使用关系数据库的新手，我正在尝试使用我在 YouTube 视频中看到的这种方法同时从 5 个表中创建一个 select 和一个 print，在第一个select 我正在选择一个人并将他的所有数据存储在包括外键在内的变量中，之后我使用存储在该人的变量中的外键从其他4个表中选择数据，最后我打印表格行上的所有数据。

我知道该方法是有效的，我已经使用它完美地从单个表中进行选择，但是在这里尝试从多个表中选择不起作用，也许我应该尝试在第一个选择中使用 JOIN 并选择所有表那里。在我运行这个 php 脚本的地方它会返回这个错误：

未定义变量：第 71 行 C:\wamp64\www\sicu\paciente.php 中的 db”和此“致命错误：在 C:\wamp64\www\sicu\ 中调用 null 时的成员函数 query() paciente.php 在第 71 行

    <?php
    $sql = "SELECT * from `paciente` ORDER BY `ci_p`";
    $result = $db-> query ($sql);

    while ($row = $result ->fetch_object()) {



    $ci_p = $row -> ci_p;
    $primer_nombre =htmlentities ($row -> primer_nombre, ENT_QUOTES, "UTF-8");
    $segundo_nombre = htmlentities ($row -> segundo_nombre, ENT_QUOTES, "UTF-8");
    $primer_apellido = htmlentities ($row ->primer_apellido , ENT_QUOTES, "UTF-8"); 
    $segundo_apellido = htmlentities ( $row -> segundo_apellido, ENT_QUOTES, "UTF-8");
    $sexo = htmlentities ( $row -> sexo, ENT_QUOTES, "UTF-8");
    $tipo_p = htmlentities ( $row -> tipo_p, ENT_QUOTES, "UTF-8");
    $tipo_personal = htmlentities ( $row -> tipo_personal, ENT_QUOTES, "UTF-8");
    $especialidad= htmlentities ( $row -> especialidad, ENT_QUOTES, "UTF-8");
    $alergias = htmlentities ( $row -> alergias, ENT_QUOTES, "UTF-8");
    $correo_id_correo = htmlentities ( $row -> correo_id_correo, ENT_QUOTES, "UTF-8");
    $telefono_id_telefono = htmlentities ( $row -> telefono_id_telefono, ENT_QUOTES, "UTF-8");
    $direccion_id_direccion = htmlentities ($row -> direccion_id_direccion , ENT_QUOTES, "UTF-8");
    $fecha_id_fecha = htmlentities ($row -> fecha_id_fecha , ENT_QUOTES, "UTF-8");

    $sql1 = "SELECT * from `direccion` where id_direccion = '$direccion_id_direccion')";
    $result1 = $db-> query ($sql1);
    while ($row1 = $result1 ->fetch_object()){
        $estado =htmlentities ($row -> estado, ENT_QUOTES, "UTF-8");
        $ciudad = htmlentities ($row -> ciudad, ENT_QUOTES, "UTF-8");
        $municipio = htmlentities ($row ->municipio , ENT_QUOTES, "UTF-8"); 
        $parroquia = htmlentities ( $row -> parroquia, ENT_QUOTES, "UTF-8");
        $sector = htmlentities ( $row -> sector, ENT_QUOTES, "UTF-8");
        $edificio = htmlentities ( $row -> edificio, ENT_QUOTES, "UTF-8");
        $piso= htmlentities ( $row -> piso, ENT_QUOTES, "UTF-8");
        $numero = $row -> numero;
        $punto_ref = htmlentities ( $row -> punto_ref, ENT_QUOTES, "UTF-8");
        $avenida = htmlentities ( $row -> fecha_ingre, ENT_QUOTES, "UTF-8");

    }
    $sql2 = "SELECT * from `correo_electronico` where id_correo = '$correo_id_correo')";
    $result2 = $db-> query ($sql2);
    while ($row2 = $result2 ->fetch_object()){
        $direccion_correo =htmlentities ($row -> direccion_correo, ENT_QUOTES, "UTF-8");

    }
        $sq3 = "SELECT * from `telefono` where id_telefono = '$telefono_id_telefono')";
    $result3 = $db-> query ($sql3);
    while ($row3 = $result3 ->fetch_object()){
    $numero_telefono = $row -> numero_telefono;

    }
        $sql5 = "SELECT * from `fecja_naci` where id_fecha_naci = '$fecha_id_fecha')";
    $result5 = $db-> query ($sql5);
    while ($row5 = $result5 ->fetch_object()){
    $fecha =htmlentities ($row -> fecha, ENT_QUOTES, "UTF-8");

    }
?>
    <tbody><tr>
        <td><?php echo $ci_p?></td>
        <td><?php echo " $primer_nombre $segundo_nombre $primer_apellido $segundo_apellido "?></td>
        <td><?php echo $sexo ?></td>
        <td><?php echo $tipo_p ?></td>
        <td><?php echo $tipo_personal?></td>
        <td><?php echo $especialidad?></td>
        <td><?php echo $alergias ?></td>
        <td><?php echo $fecha?></td>
        <td><?php echo $numero_telefono?></td>
        <td><?php echo $direccion_correo?></td>
        <td><?php echo "$estado $ciudad $municipio $parroquia $sector $edificio $piso $numero $punto_ref $avenida"?></td>
    </tr></tbody>
<?php
}
?>

Answer 1

首先，建立一个文件connection.php

<?php

$db = new mysqli("Host name","User","DB Password","DB Name");

// ceck connection

if ($db->connect_error) {
   die('Connection failed: '. $connect->connect_error);
}
?>

然后添加这段代码：

include "connection.php";

在你的 php 文件中。

我的建议是在 mysql 中使用内连接