Question

我花了整整一个晚上研究并试图弄清楚我的搜索查询有什么问题。我使用联合查询和分页进行一些通配符搜索。

$current_page = 0;

$search1 = $search;
$search2 = $search."%";
$search3 = "%".$search."%";

$pdo = DB::connection()->getPdo();

$stmt = $pdo->prepare('
    SELECT id, desc FROM table WHERE desc LIKE :search1 LIMIT :skip, 15
    UNION
    SELECT id, desc FROM table WHERE desc LIKE :search2 LIMIT :skip, 15
    UNION
    SELECT id, desc FROM table WHERE desc LIKE :search3 LIMIT :skip, 15
');

$stmt->bindParam(':search1', $search1);
$stmt->bindParam(':search2', $search2);
$stmt->bindParam(':search3', $search3);
$stmt->bindParam(':skip', $current_page, PDO::PARAM_INT);

$stmt->execute();

$result = $stmt->fetchAll(PDO::FETCH_ASSOC);

第一个查询（没有联合）工作正常，或者如果我删除：skip参数，它也能正常工作。

任何想法有什么不对？

Answer 1

在PDO中使用命名参数，除非您执行以下操作，否则不能多次使用相同的名称：

$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);

但是如果这样做，:skip的值将作为带引号的字符串内插到查询中，这在LIMIT的上下文中无效。换句话说如下：

LIMIT '0', 15

导致语法错误，因为LIMIT只想要真正的整数作为其参数。

有关更多示例和说明，请参阅我对Parametrized PDO query and LIMIT clause - not working

的回答

因此，您可以选择为:skip的每次出现添加一个单独的参数：

$stmt = $pdo->prepare('
    SELECT id, desc FROM table WHERE desc LIKE :search1 LIMIT :skip1, 15
    UNION
    SELECT id, desc FROM table WHERE desc LIKE :search2 LIMIT :skip2, 15
    UNION
    SELECT id, desc FROM table WHERE desc LIKE :search3 LIMIT :skip3, 15
');

$stmt->bindParam(':search1', $search1);
$stmt->bindParam(':search2', $search2);
$stmt->bindParam(':search3', $search3);
$stmt->bindParam(':skip1', $current_page, PDO::PARAM_INT);
$stmt->bindParam(':skip2', $current_page, PDO::PARAM_INT);
$stmt->bindParam(':skip3', $current_page, PDO::PARAM_INT);

或者自己将值插入到查询中，不用引用整数。

但我同意@Class的评论，你根本不需要做UNION。如果不出意外，'%search%'适用于其他两种模式：'search%'和'%search'。您不必搜索所有三个。

Answer 2

将每个SELECT括在括号中。

来自documentation

要将ORDER BY或LIMIT应用于单个SELECT，请将该子句放在括起SELECT的括号内：

$stmt = $pdo->prepare('
    (SELECT id, desc FROM table WHERE desc LIKE :search1 LIMIT :skip, 15)
    UNION
    (SELECT id, desc FROM table WHERE desc LIKE :search2 LIMIT :skip, 15)
    UNION
    (SELECT id, desc FROM table WHERE desc LIKE :search3 LIMIT :skip, 15)
');

Answer 3

就像更新一样，如果有人在这里试图实现类似的搜索，通过相关性返回结果，上面的原始查询将复制一些结果，每个选择的限制将跳过一些结果。

经过一些测试后，以下查询似乎按预期完成了工作：

$current_page = ($_GET['page'] - 1) * 15;

$search1 = $search;
$search2 = $search."%";
$search3 = "%".$search."%";

$pdo = DB::connection()->getPdo();

$stmt = $pdo->prepare('
    SELECT id, desc FROM table WHERE desc LIKE :search1
    UNION
    SELECT id, desc FROM table WHERE desc LIKE :search2 AND desc NOT LIKE :search1a
    UNION
    SELECT id, desc FROM table WHERE desc LIKE :search3 AND desc NOT LIKE :search2a
    LIMIT :skip, 15
');

$stmt->bindParam(':search1', $search1);
$stmt->bindParam(':search1a', $search1);
$stmt->bindParam(':search2', $search2);
$stmt->bindParam(':search2a', $search2);
$stmt->bindParam(':search3', $search3);
$stmt->bindParam(':skip', $current_page, PDO::PARAM_INT);

$stmt->execute();

$result = $stmt->fetchAll(PDO::FETCH_ASSOC);

PDO - SQLSTATE [HY093]：UNION查询的参数号无效

3 个答案: