当表为空时，如何避免异常？

I want to fetch one single value from my database. Therefore I use the following code:

我想从我的数据库中获取一个值。因此我使用以下代码:

$qb->select('u.userId')
   ->from('user', 'u')
   ->orderBy('u.id', 'DESC')
   ->setMaxResults(1);
$query = $qb->getQuery();
$result = $query->getSingleResult();

The code works fine if there is at least one row in that table. But if the table is empty it throws an exception. How can I intercept this exception?

如果该表中至少有一行,则代码可以正常工作。但是如果表是空的,它会抛出异常。我如何拦截此异常?

I tried stuff like if($result->isEmpty(), $result === null or empty($result) but my exception seems to be thrown at line no. 3 in the example above, so I can't intercept it afterwards.

我试过像if($ result-> isEmpty(),$ result === null或empty($ result)这样的东西但我的异常似乎是在上面的例子中的第3行抛出,所以我无法拦截它然后。

1 个解决方案

#1

This should work.

这应该工作。

IF EXISTS(<query>)
  SELECT 'not empty'
ELSE
  SELECT 'empty'