I'm trying to retrieve single column from my table grades.
For that I have used following code in my controller:
public function verify($id,$sid)
all() takes a list of columns to load from the database. In your case, you're fetching only one column called annual, therefore filtering on id later on does not return results. Replace your code with the following and it should work:
$grade = Grade::all('id', 'annual')->whereLoose('id', $id);
Keep in mind that it will return a collection of objects, not a single object.
NOTE: you're always loading all Grade objects from the database which is not efficient and not necessary. You can simply fetch object with given id with the following code:
$grade = Grade::find($id); // fetch all columns $grade = Grade::find($id, ['id', 'annual']); // fetch only selected columns