How to get all the records where a column shoud be unique

SQL++
1

I want to fetch all the records from bucket where a column should be unique like,
I have 3 records ,

{
“discount_code”:“SAVE20”,
“discount_price”:“20%”,
“start_discount_date”:“2019-12-17”,
“end_discount_date”:“2019-12-25”
}
{
“discount_code”:“SAVE20”,
“discount_price”:“20%”,
“start_discount_date”:“2019-12-15”,
“end_discount_date”:“2019-12-20”
}
{
“discount_code”:“SAVE10”,
“discount_price”:“10%”,
“start_discount_date”:“2019-12-12”,
“end_discount_date”:“2019-12-25”
}

Now i want all the records date between 2019-12-15 to 2019-12-25,
I get all the values which repeats discount_code:SAVE20 two times.
How can i get all records where with unique value of discount_code?

2 
SELECT  DISTINCT d.discount_code
FROM default AS d
WHERE  d.start_discount_date BETWEEN "2019-12-15" AND "2019-12-25" 
                   AND d.end_discount_date BETWEEN "2019-12-15" AND "2019-12-25" ;

OR

If same discount code but other values are different and want to all the documents.

 SELECT  DISTINCT d.*
    FROM default AS d
    WHERE  d.start_discount_date BETWEEN "2019-12-15" AND "2019-12-25" 
                       AND d.end_discount_date BETWEEN "2019-12-15" AND "2019-12-25" ;

OR

  SELECT   RAW d
        FROM default AS d
        WHERE  d.start_discount_date BETWEEN "2019-12-15" AND "2019-12-25" 
                           AND d.end_discount_date BETWEEN "2019-12-15" AND "2019-12-25" 
    GROUP BY d;

OR

SELECT   ARRAY_AGG( DISTINCT d) AS docs
    FROM default AS d
    WHERE  d.start_discount_date BETWEEN "2019-12-15" AND "2019-12-25" 
                       AND d.end_discount_date BETWEEN "2019-12-15" AND "2019-12-25" 
GROUP BY d.discount_code;