mysql_num_rows返回null每次

Question

if (isset($_GET["val"])) { 
    $val = $_GET["val"]; 
    $sql1 = "select count(*) as count from staff_log l where l.time_in is null and l.time_out is not null and l.date_today = curdate() and l.staff_id = ".$val.";"; 

    $result1 = mysql_num_rows($sql1); 
} 

Answer 1

加入這一行...

$result = mysql_query($sql1); 
$result1 = mysql_num_rows($result); 

必須在mysql_query()功能定義查詢;

Answer 2

mysql_num_rows()返回，如在PHP manual所示：

行中一個結果集上或FALSE的成功失敗的次數。

這意味着執行它時出錯，這顯然是因爲您沒有運行任何查詢（mysql_query()）。

注意，PHP手冊也有在頁面的頂部以下警告：

這個擴展被廢棄在PHP 5.5.0，它是PHP 7.0.0中刪除。相反，應該使用MySQLi或PDO_MySQL擴展。

Answer 3

首先執行查詢，然後NUM_ROWS

原來的MySQL擴展現在已經過時，並連接到數據庫時，會產生E_DEPRECATED錯誤。而是使用MYSQLi或PDO_MySQL擴展。

試試這個

if (isset($_GET["val"])) 
{ 
$val = $_GET["val"]; 
$sql1 = "select count(*) as count from staff_log l where l.time_in is null and l.time_out is not null and l.date_today = curdate() and l.staff_id = ".$val.";"; 

$result = mysql_query($sql1); 
$count = mysql_num_rows($result); 

} 

Answer 4

你幾乎權利，請查看下面的代碼。您需要使用mysql_query（），mysql_query（）用於執行默認數據庫的查詢。

if (isset($_GET["val"])) 
{ 
    $val = $_GET["val"]; 
    $sql1 = "select count(*) as count from staff_log l where l.time_in is null and l.time_out is not null and l.date_today = curdate() and l.staff_id ='$val'"; 
    $sql2 = mysql_query($sql1); // Execute the query first 
    $result1 = mysql_num_rows($sql2); // Get the number of rows from executed query result. 
    echo "The count is $result1"; 
}