查询计数值

Question

我在MySQL中有两个表：

人

|ID  | Name    |  Address
---------------------------------
| 1  | Someone |  Somewhere
| 2  | Person2 |  Somewhere else

表ActivePages

|ID  | PersonID |  Page
---------------------------------------
| 1  | 1        |  somepage
| 1  | 1        |  someotherpage

现在我需要一个查询来返回以下内容：

|PersonID | Count
------------------
|1        | 2
|2        | 0
------------------

谁可以帮我这个？我认为它是直截了当的，但我一直得到错误的价值......

提前致谢！

Answer 1

   SELECT p.ID AS PersonID,
          COUNT(a.PersonID) AS `Count`
     FROM Persons p
LEFT JOIN ActivePages a ON a.PersonID = p.ID
 GROUP BY p.ID

Answer 2

    select personid,count(personid) as count from activepages
     right join Persons on ActivePages.PersonID = Persons.ID group by personid