mysql - 一个查询中的嵌套计数

Question

我需要计算每种消息表类型的未读消息数量。

表: 消息

领域：

Id Message Type Unread
1   xxxxx   0    0
2   xxxxx   1    0
3   xxxxx   1    0
4   xxxxx   1    1
5   xxxxx   2    0
6   xxxxx   3    0
7   xxxxx   3    1

所以，我需要这样的结果：

For type 0 there is 1 unread message, and a total of 1 message.
For type 1 there are 2 unread messages, and a total of 3 messages.
For type 2 there is 1 unread message, and a total of 1 message.
For type 3 there is 1 unread message, and a total of 2 messages.

到目前为止，我能够计算每种类型有多少条消息：

SELECT 
    `message_type`, 
    COUNT(`message_type`) AS message_type_count
FROM 
    Messages
GROUP BY `message_type`

但是，我还需要每种类型的未读消息数量。我怎样才能做到这一点？

谢谢你的帮助！

Answer 1

SELECT message_type,
       COUNT(message_type) AS message_type_count,
       SUM(Unread = 1) AS unread_count
FROM Messages 
GROUP BY message_type