如何从多个 table 中获取数据

Question

我有三个不同的表，我们将它们命名为

表1, 表 2, 表 3

但是在这些不同的表中，我有相同的列数和相同的名称。例如，

Table 1 列：id、标题、类别、子类别、图片
Table 2列：id, title, category, subcategory, image
Table 3列：id, title, category, subcategory, image

如何使用单个 foreach 获取所有这 3 个表？

function post_details(){
  global $db;
  $query = "SELECT * FROM posts WHERE status = 'Active' ORDER BY id DESC";
  $run_query = mysqli_query($db, $query);
  $post_details = mysqli_fetch_all($run_query, MYSQLI_ASSOC);
  $getdetails = array();
  
  foreach ($post_details as $post_detail) {
    array_push($getdetails, $post_detail);
  }

  return $getdetails;
}

Answer 1

如果您的页面显示空白，请将其添加到 php 文件的顶部

//if error happend,this will display error on page
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

如果你想简单地循环行，你可以使用mysql union

function post_details(){
    global $db;
    $query = "SELECT * FROM posts1 WHERE status = 'Active' ORDER BY id DESC";
    $query .= " UNION SELECT * FROM posts2 WHERE status = 'Active' ORDER BY id DESC";
    $query .= " UNION SELECT * FROM posts3 WHERE status = 'Active' ORDER BY id DESC";
    $run_query = mysqli_query($db, $query);
    $post_details = mysqli_fetch_all($run_query, MYSQLI_ASSOC);
    $getdetails = array();
    
  foreach ($post_details as $post_detail) {
        array_push($getdetails, $post_detail);
    }

    return $getdetails;
}

如果你想按所有人排序 table 你可以像这样使用临时 table，注意这一点，在大数据集中它可能会很慢，因为它排序临时 table.

$query = "SELECT * FROM 
            (SELECT * FROM posts1 WHERE status = 'Active'  
                UNION SELECT * FROM posts2 WHERE status = 'Active' 
                UNION SELECT * FROM posts3 WHERE status = 'Active') 
            AS t1 ORDER BY id DESC";

Answer 2

实际上，当我们想从多个table中获取具有相同列或相同table但条件不同的记录时，我们需要使用 UNION 将所有这些记录合并到相同的 SQL 查询，因此请使用此查询并将 table 名称替换为您的真实 table 名称。

$query = "SELECT * FROM ( ( SELECT * FROM table1 WHERE status = 'Active' ORDER BY id DESC ) 
UNION 
( SELECT * FROM table2 WHERE status = 'Active' ORDER BY id DESC ) 
UNION 
( SELECT * FROM table2 WHERE status = 'Active' ORDER BY id DESC ) ) as tempdata";

如何从多个 table 中获取数据

How to fetch datas from multiple table

php

mysqli