SQL COUNT（）在MySQL中不起作用

Question

SELECT person.id,
       person.name,
       COUNT(DISTINCT fruit.apple) AS "Red Apple",
       fruit.*
FROM   (SELECT *
        FROM   tree
        ORDER  BY color DESC) AS fruit
       INNER JOIN person
         ON fruit.id = person.id
WHERE  person.name = 'John Smith'  

Now, that code is working before I put in the COUNT(DISTINCT fruit.apple) AS "Apple" . what is wrong with that?

Thanks in advance

Answer 1

您没有group by子句。

Answer 2

try this

SELECT person.id,
       person.name,
       COUNT(DISTINCT fruit.apple) AS "Red Apple",
       fruit.*
FROM   (SELECT *
        FROM   tree
        ORDER  BY color DESC) AS fruit
       INNER JOIN people
         ON fruit.id = person.id
WHERE  person.name = 'John Smith' 
GROUP BY fruit.apple