Question

将此SQL语句编写为PDO查询的最佳方法是什么？我希望它以数字形式返回查询数。

SELECT  COUNT(*) totalCount
FROM    ts_room a
        INNER JOIN ts_roompref b
            ON a.id = b.room_ID
        INNER JOIN ts_request c
            ON b.request_ID = c.roompref_ID
WHERE   c.day_ID = 1 AND c.period_ID = 1

这就是我的想法：

$room_ID = $_POST["room"];

$sql = "SELECT  COUNT(*) totalCount
FROM    ts_room a
        INNER JOIN ts_roompref b
            ON a.id = b.:room_ID
        INNER JOIN ts_request c
            ON b.request_ID = c.roompref_ID
WHERE   c.day_ID = 1 AND c.period_ID = 1";

$stm = $pdo->prepare( $sql );
$stm->execute( array( ':room_ID' => $room_ID) );
$rows = $stm->fetchAll();

// echo row count here
$count = $stm->rowCount();

Answer 1

如果要获取总行数，请使用fetchColumn函数。

还有一个更正，因为您在 ON子句中使用 JOIN ，所以不能使用变量值，只使用列名。

$room_ID = $_POST["room"];

$sql = "SELECT  COUNT(*) totalCount
FROM    ts_room a
        INNER JOIN ts_roompref b
            ON a.id = b.room_ID
        INNER JOIN ts_request c
            ON b.request_ID = c.roompref_ID
WHERE   c.day_ID = 1 AND c.period_ID = 1 and b.room_ID=:room_ID";

$stm = $pdo->prepare( $sql );
$stm->execute( array( ':room_ID' => $room_ID) );
$rows = $stm->fetchColumn();

Answer 2

请检查一下你的查询：我已经高估了你做错的情况，这将放在where子句中。

  SELECT  COUNT(*) totalCount
    FROM    ts_room a
            INNER JOIN ts_roompref b
                 // ON a.id = b.:room_ID
            INNER JOIN ts_request c
                ON b.request_ID = c.roompref_ID
    WHERE   c.day_ID = 1 AND c.period_ID = 1

我猜您的代码将如下所示：

$ room_ID = $ _POST [“room”];

$sql = "SELECT  COUNT(*) totalCount
FROM    ts_room a
        INNER JOIN ts_roompref b
            ON a.id = b.room_ID
        INNER JOIN ts_request c
            ON b.request_ID = c.roompref_ID
WHERE   c.day_ID = 1 AND c.period_ID = 1 and b.room_ID=:room_ID";

$stm = $pdo->prepare( $sql );
$stm->execute( array( ':room_ID' => $room_ID) );
$rows = $stm->fetchAll();

在PDO查询中使用COUNT和内部联接

2 个答案: