区分联合中的两个查询

Question

在以下联合查询示例中，我如何区分记录的来源：

SELECT id, name, datetime FROM events
UNION
SELECT id, name, datetime FROM festival
ORDER BY datetime DESC

我在 PHP 中的使用方式是：

$stmt = $cxn->prepare('SELECT id, name, datetime FROM events WHERE id = ? UNION SELECT id, name, datetime FROM festival WHERE id = ? ORDER BY datetime DESC');
$stmt->bind_param('i', $event_id);
$stmt->execute();
$stmt->store_result();
$stmt->bind_result($id, $name, $datetime);

while ($stmt->fetch()) {
    echo "ID: " . $id . "\n";
    echo "Name: " . $name . "\n";
    echo "Date: " . $datetime;
}

$stmt->close();

Answer 1

SELECT id, name, datetime, 'events' FROM events
UNION
SELECT id, name, datetime, 'festival' FROM festival
ORDER BY datetime DESC

PHP

$stmt = $cxn->prepare('SELECT id, name, datetime, "events" as tablename FROM events WHERE id = ? UNION SELECT id, name, datetime, "festival" as tablename FROM festival WHERE id = ? ORDER BY datetime DESC');
$stmt->bind_param('i', $event_id);
$stmt->execute();
$stmt->store_result();
$stmt->bind_result($id, $name, $datetime, $table);

while ($stmt->fetch()) {
    echo "ID: " . $id . "\n";
    echo "Name: " . $name . "\n";
    echo "Date: " . $datetime;
    echo "Which Table: " . $table;
}

$stmt->close();

Answer 2

您可以通过再添加一列并将其区分为：

SELECT id, name, datetime, 'E' as fromwhere FROM events
UNION
SELECT id, name, datetime,'F' as fromwhere FROM festival
ORDER BY datetime DESC

fromwhere 列会告诉您它是来自活动还是节日。