获取具有相同列数据的多个表

Question

i have three table with same value of columns. example: say i have three table " table1 ", " table2 ", " table3 " and each columns has " id ", " title ", " description ", " category ", " date ", " thumbnail ", " admin ". now i'm trying to get all data from those three table. but there is a think, i want to check with if statement . if table1 not match with id, check table2 . if table2 not match with id, check table3 and at last show the data. please check my below code, i'm trying to get data from those three table:

<?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'];
         }
          ?>

please help me to get all data from those three table with if statement it will be better to understand if you post an answer. thank you in advance.

Answer 1

Use a UNION of 3 queries.

$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'];
}

Adding the tnum column to the result orders them so the table1 data is preferred, then table2 , finally table3 .