PHP PDO获取null [英] PHP PDO fetch null

问题描述

如何检查列值是否为空?示例代码:

How do you check if a columns value is null? Example code:

$db = DBCxn::getCxn();

$sql = "SELECT exercise_id, author_id, submission, result, submission_time, total_rating_votes, total_rating_values
FROM submissions 
LEFT OUTER JOIN submission_ratings ON submissions.exercise_id=submission_ratings.exercise_id
WHERE id=:id";

$st = $db->prepare($sql);

$st->bindParam(":id", $this->id, PDO::PARAM_INT);

$st->execute();
$row = $st->fetch();

$this->total_rating_votes = $row['total_rating_votes'];

if($this->total_rating_votes == null) // this doesn't seem to work even though there is no record in submission_ratings????
{
...
}

推荐答案

感谢您的所有回答.经过一番实验后，这段代码解决了我的问题

Thanks for all of your answers. After a bit of experimentation this code solved my problem

$this->total_rating_votes = $row['total_rating_votes'];

if(!isset($this->total_rating_votes)) // this is now true if this record had a NULL value in the DB!!!
{
...
}

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