如何在 GROUP_CONCAT 中使用选择别名？

Question

1. I am averaging 4 columns and giving an alias score .
2. Now, I am trying to use score alias inside GROUP_CONCAT to get rank .
3. Everything works except when I add (SELECT GROUP_CONCAT( score ORDER BY score DESC) FROM math )) AS rank .
4. I understand it does not work because score does not exist in the math table. But what do I need to do to make it work?

Here is my query in laravel 5.5 -

$ranking = DB::select('SELECT id, (a.addition_accuracy + a.subtraction_accuracy + a.multiplication_accuracy + a.division_accuracy)/4 as score, (SELECT GROUP_CONCAT( score ORDER BY score DESC) FROM math )) AS rank FROM math a where level = 5');

1. I get 500 server error from above query.
2. I am expecting below output

    {
        "id": 38,
        "score": 99.24250030517578,
        "rank": 1

    },
    {
        "id": 51,
        "score": 84.88500213623047,
        "rank": 2
    },
    {
        "id": 204,
        "score": 69.27500057220459,
        "rank": 3
    }
]```

Answer 1

Try this one for your query. I changed it to checl also the score

SELECT 
  id
  , (a.addition_accuracy + a.subtraction_accuracy + a.multiplication_accuracy + a.division_accuracy)/4 as score
  ,if(@score = score,@rank:= @rank,@rank:= @rank+1) as rank
  ,  @score := score
  FROM math a,(SELECT @rank :=0) b ,(SELECT @score :=0) c
  where level = 5
  ORDER BY score DESC
LIMIT 3

As i said some data as test ground would be nice