我有一个查询，搜索三件事，一个关键字，一个类别和一个地区（它的空缺）。除了区域之外，所有的东西都能工作，因为我从数据库中得到了一个别名为的列。
我的代码现在：

$functie = $_POST['functie'];
$branche = $_POST['branche'];
$regio = $_POST['regio'];

$search = "
SELECT cnt.title as content_title, cnt.alias as content_alias, cnt.images, cnt.introtext, cnt.catid, cat.title as cat_title, cat.alias as cat_alias,
MAX(case when f.field_id = 2 then f.value end) as regio
FROM snm_content cnt
LEFT JOIN snm_categories cat
ON cat.id = cnt.catid
LEFT JOIN snm_fields_values f
ON cnt.id = f.item_id
";
// Collect all the where conditions in an array
$whr = array();

// check if $functie has some value in input filter
if (!empty($functie)) {
    $whr[] = "cnt.title LIKE '%" . $functie . "%'";
}

if (!empty($regio)) {
    $whr[] = "f.value LIKE '%" . $regio . "%'";
}

// check if $branche has some value in input filter
if (!empty($branche)) {
    $whr[] = "cat.title LIKE '%" . $branche . "%'";
}

$where_sql = '';
// Prepare where part of the SQL
if (!empty($whr)) {

    $where_sql = ' WHERE ' . implode(' OR ', $whr);
}

// Append to the original sql
$search .= $where_sql;
$searchcon = $conn->query($search);

但上述代码并不适用于该地区。
不过，这是endresult查询，我得到的结果如下：

SELECT cnt.title as content_title, cnt.alias as content_alias, cnt.images, cnt.introtext, cnt.catid, cat.title as cat_title, cat.alias as cat_alias,
MAX(case when f.field_id = 2 then f.value end) as regio
FROM snm_content cnt
LEFT JOIN snm_categories cat
ON cat.id = cnt.catid
LEFT JOIN snm_fields_values f
ON cnt.id = f.item_id
WHERE cnt.title LIKE '%vrachtwagen%'

regio 是我想展示结果的原因。
但是 WHERE regio LIKE '%" . $regio . "%'"; 不起作用，它说未知列 regio 因为它是一个别名。如何仅显示所发布区域的所有结果？例如上图，当 Drenthe 是发布的区域。