Question

一直关注我在网上找到的这个php / mysql教程，现在我无法让这个查询起作用。我相信的问题是在从select查询返回null resultset之后使用insert查询。

$new_start_no = isset($_POST['start_no']) ? $_POST['start_no'] : '';
$new_end_no = isset($_POST['end_no']) ? $_POST['end_no'] : '';
$new_job_no = isset($_POST['job_no']) ? $_POST['job_no'] : '';

$query = "SELECT COUNT (*)"; 
$query .= "FROM jobs";
$query .= "WHERE job_no=$new_job_no"; 
$query .= "AND start_no <= $new_end_no";
$query .= "AND end_no >= $new_start_no";
$result = mysqli_query($connection, $query);
$num_rows = mysqli_num_rows($result);
if (is_null) { 
$query = "INSERT INTO jobs (";
 $query .= " user_id, start_no, end_no, start_date, client_name, card_type, job_no, job_quantity, end_date, shred_option";
 $query .= ") VALUES (";
 $query .= " '{$user_id}', '{$start_no}', '{$end_no}', '{$start_date}', '{$client_name}', '{$card_type}', '{$job_no}', '{$job_quantity}', '{$end_date}', '{$shred_option}'";
 $query .= ")";
 $result = mysqli_query($connection, $query);
 if ($result) {
// success
   $_SESSION["message"] = "job created.";
   redirect_to("manage_job.php"); 
  } else {
// failure  
   $_SESSION["message"] = "job creation failed.";
   redirect_to("new_job.php");
  }  
}

Answer 1

您的查询总是返回1行，因为它使用COUNT(*)来计算匹配的行。您需要检索该行并从中获取计数。您应该为计数指定别名，以便检索它。然后你需要测试计数，而不是is_null。

$query = "SELECT COUNT (*) AS ct"; 
$query .= "FROM jobs";
$query .= "WHERE job_no=$new_job_no"; 
$query .= "AND start_no <= $new_end_no";
$query .= "AND end_no >= $new_start_no";
$result = mysqli_query($connection, $query);
$row = mysqli_fetch_assoc($result);
$num_rows = $row['ct'];
if ($num_rows == 0) {
    // INSERT code
} else {
    $_session["message"] = "job no is not available";
}

执行SELECT查询并检查是否返回任何行以及是否为空结果集执行INSERT

1 个答案: