PDO准备陈述“哪里”问题

Question

我是PDO新手，我正努力在准备好的语句中使用“ where”语句。 下面是我尝试的代码。 它返回无法从数据库检索数据。

谁能告诉我问题是什么？ 有什么可以尝试的吗？

赞赏！

$user_id = 1;

try {
    $query = $db->prepare("
            SELECT title, img, id
            FROM listings
            ORDER BY id DESC
            WHERE userID = :user_id
            LIMIT 2");
$query->bindParam(':user_id', $user_id, PDO::PARAM_INT);
$query->execute();

} catch (Exception $e) {
    echo "Data could not be retrieved from the database.";
    exit;
} 

$data = $query->fetchAll( PDO::FETCH_ASSOC);

return $data;

更新：我交换了order ＆ where子句，但它仍然不返回任何内容（与上一个错误消息相反）。

Answer 1

像这样重写您的查询。 [ 您需要在WHERE之后放置ORDER BY子句 ]

   $query = $db->prepare("
            SELECT title, img, id
            FROM listings
            WHERE userID = :user_id
            ORDER BY id DESC
            LIMIT 2");

Answer 2

where条件之后需要添加ORDER BY id DESC 。

$query = $db->prepare("
            SELECT title, img, id
            FROM listings               
            WHERE userID = :user_id
            ORDER BY id DESC
            LIMIT 2");

Mysql Generic Select语法：

   SELECT
    [ALL | DISTINCT | DISTINCTROW ]
      [HIGH_PRIORITY]
      [STRAIGHT_JOIN]
      [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
      [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
    select_expr [, select_expr ...]
    [FROM table_references
    [WHERE where_condition]
    [GROUP BY {col_name | expr | position}
      [ASC | DESC], ... [WITH ROLLUP]]
    [HAVING where_condition]
    [ORDER BY {col_name | expr | position}
      [ASC | DESC], ...]
    [LIMIT {[offset,] row_count | row_count OFFSET offset}]
    [PROCEDURE procedure_name(argument_list)]
    [INTO OUTFILE 'file_name' export_options
      | INTO DUMPFILE 'file_name'
      | INTO var_name [, var_name]]
    [FOR UPDATE | LOCK IN SHARE MODE]]

Answer 3

where子句应该在order子句之前

$query = $db->prepare("
            SELECT title, img, id
            FROM listings
            WHERE userID = :user_id
            ORDER BY id DESC
            LIMIT 2");