如何在查询结果中添加类别？

Question

I have the following query:

SELECT date, fruit, COUNT(id) AS count
FROM fruits
GROUP BY date, fruit

that gives the following results:

date           fruit      count
--------------------------------
2020-10-03     apple        3
2020-10-03     orange       5
2020-10-04     apple        23
2020-10-04     orange       1
2020-10-05     apple        10
2020-10-05     orange       6

Is it possible, and if so, how, to add a new fruit to the above results mango if it does not exist for every date with count=0 , as shown below?

date           fruit      count
--------------------------------
2020-10-03     apple        3
2020-10-03     orange       5
2020-10-03     mango        0
2020-10-04     apple        23
2020-10-04     orange       1
2020-10-04     mango        0
2020-10-05     apple        10
2020-10-05     orange       6
2020-10-05     mango        0

Answer 1

With UNION ALL :

SELECT date, fruit, COUNT(id) AS count
FROM fruits
GROUP BY date, fruit
UNION ALL
SELECT DISTINCT f.date, 'mango', 0
FROM fruits f
WHERE NOT EXISTS (SELECT 1 FROM fruits WHERE date = f.date AND fruit = 'mango')