UNION 查询问题

Question

我正在尝试对我的数据库中的两个表进行看似简单的联合查询，尽管我无法检索到成功的数组结果。应该注意的是，每个表都有不同的列，我想创建一个虚拟结果（promo AS origin [对于从 'venpromo' 表中提取的结果] && holiday AS origin [对于从'vacation 中提取的结果' table]) 以便将结果排序到不同的数组结构中。我到处寻找，UNIONS 都使用不同的语法。提前谢谢大家！

<?php
    require_once('includes/config.php');

    $event_query = "SELECT *, promo AS origin FROM venpromo
    UNION 
    SELECT *, vacation AS origin FROM venpromo 
    ORDER BY popularity DESC";
    $event_result = mysql_query($event_query, $connection);
    while ($event = mysql_fetch_array($event_result)) {
        if ($event['origin'] == "promo") {
            $event_array[] = array(
                'id' => $event['id'],
                'title' => $event['calname'],
                'start' => $event['sdate'],
                'end' => $event['edate'],
                'color' => "red",
                'url' => "http://www.norrisportal.com/bulletinpost.php?id=" . $event['id'] . "&hashkey=akdULjsjyUpYyTzOT7"
            );
        } elseif ($event['origin'] == "vacation") {
            $event_array[] = array(
                'id' => $event['id'],
                'title' => $event['reason'],
                'start' => $event['vacstart'],
                'end' => $event['vacend'],
                'color' => "blue"
            );
        }
    }

    echo json_encode($event_array);

?>

访问页面查看结果时，我看到“null”。

Answer 1

明确输入列名而不是 *，并确保每个选择中同一列的列数和数据类型匹配。

我添加了一些虚拟列来匹配两个表中的数字和数据类型，并更改了列的顺序。

试试这个示例方法::

select 
id,
uid,
approval,
vacstart,
vacend,
reason,
'dummy1' col1,
'dummy2' col2,
'dummy3' col3,
curdate() col4,
'dummy4' col5,
'dummy5' col6,
'dummy6' col7,
'dummy7' col8,
promo AS origin
from vacation
union
select
id,
venid,
authid,
sdate,
edate,
authname,
tags,
title,
calname,
date,
intro,
body,
sum,
sortdate,
vacation AS origin
from venpromo;