获取具有相同列数据的多个表

Question

我有三个具有相同列值的表。例如：假设我有三个表“table1”、“table2”、“table3”，每列都有“id em>”、“标题”、“描述”、“类别”、“日期”、“缩略图”、“管理员”。现在我正在尝试从那些 三个 表中获取所有数据。但有一个想法，我想检查一下 if 语句。如果 table1 与 id 不匹配，请检查 table2。如果 table2 与 id 不匹配，请检查 table3 并最后显示数据。请检查我下面的代码，我正在尝试从这三个表中获取数据：

<?php
            include('config/database.php');
            $id=$_GET['single'];
            $query=mysqli_query($conn,"select * from table1, table2, table3 where id='$id'  ");
            while($row=mysqli_fetch_array($query)){
            $title=$row['title'];
            $date=$row['date'];
            $admin=$row['admin'];
            $thumbnail=$row['thumbnail'];
            $description=$row['description'];
            $category=$row['category'];
         }
          ?>

请帮助我使用 if 语句 从这三个表中获取所有数据 如果您发布答案会更好地理解。提前谢谢你。

Answer 1

使用 3 个查询中的 UNION。

$sql = "
    SELECT * FROM (
        SELECT 1 AS tnum, * FROM table1 WHERE id = ?
        UNION ALL
        SELECT 2 AS tnum, * FROM table2 WHERE id = ?
        UNION ALL
        SELECT 3 AS tnum, * FROM table3 WHERE id = ?
    ) AS x
    ORDER BY tnum
    LIMIT 1";
$stmt = $conn->prepare($sql);
$stmt->bind_param('iii', $id, $id, $id);
$stmt->execute();
$result = $stmt->get_result();
$row = $result->fetch_assoc();
if ($row) {
    $title = $row['title']
    $date=$row['date'];
    $admin=$row['admin'];
    $thumbnail=$row['thumbnail'];
    $description=$row['description'];
    $category=$row['category'];
}

将tnum 列添加到结果中对它们进行排序，因此首选table1 数据，然后是table2，最后是table3。

Answer 2

<?php

include "config/database.php";
$id = $_GET["single"];

$query1 = "SELECT * from table1 where id='$id'";
$res1 = $db->query($query1);
foreach ($res1 as $row) {
  $id2 = $row["id"];
  if ($id == $id2) {
    $title = $row["title"];
    $date = $row["date"];
    $admin = $row["admin"];
    $thumbnail = $row["thumbnail"];
    $description = $row["description"];
    $category = $row["category"];
    // Then echo data
  } elseif ($id != $id2) {
    $query2 = "SELECT * from table1 where id='$id'";
    $res2 = $db->query($query2);
    foreach ($res2 as $row2) {
        $id3 = $row["id"];
        if ($id == $id3) {
            $title = $row["title"];
            $date = $row["date"];
            $admin = $row["admin"];
            $thumbnail = $row["thumbnail"];
            $description = $row["description"];
            $category = $row["category"];
            // then echo data
        } elseif ($id != $id3) {
            $query3 = "SELECT * from table1 where id='$id'";
            $res3 = $db->query($query2);
            foreach ($res3 as $row3) {
                $id3 = $row3["id"];
                if ($id == $id3) {
                    $title = $row["title"];
                    $date = $row["date"];
                    $admin = $row["admin"];
                    $thumbnail = $row["thumbnail"];
                    $description = $row["description"];
                    $category = $row["category"];
                    // then echo data
                }
            }
        }
    }
}

} ?>