Mysql 在一个选择上显示2计数语法

我有一张书单上的桌子

+---------+-------------------------+------------------+-------------+-------+----------+
| ID      | Title                   | Writer           | Publisher   | year  | Status   |
+---------+-------------------------+------------------+-------------+-------+----------+
| S00001  | philosophy the intro    | K. Bertens.      | Kanisius    | 2018  | BOOKED   |
| S00002  | Karl Marx: Das Kapital  | Karl Marx        | el-Classica | 2017  | READY    |
| S00003  | Karl Marx: Das Kapital  | Karl Marx        | el-Classica | 2017  | READY    |
| S00004  | Karl Marx: Das Kapital  | Johann Luwiss    | Mediatama   | 2015  | READY    |
| S00005  | Marxis                  | Karl Marx        | Photoem     | 2019  | READY    |
| S00006  | Karl Marx: Das Kapital  | Karl Marx        | el-Classica | 2017  | BOOKED   |
| S00007  | philosophy the intro    | K. Bertens.      | Kanisius    | 2018  | READY    |
+---------+-------------------------+------------------+-------------+-------+----------+

首先，我可以按标题和作者显示标题和作者组副本的计数，但我无法显示每行“就绪”状态的计数

结果应该是这样的

+-------------------------+-----------------+-------+------+
| Title                   | Writer          | Ready | stock|
+-------------------------+-----------------+-------+------+
| Marxis                  | Karl Marx       | 1     |    1 |
| Karl Marx: Das Kapital  | Johann Luwiss   | 1     |    1 |
| Karl Marx: Das Kapital  | Karl Marx       | 2     |    3 |
| philosophy the intro    | K. Bertens.     | 1     |    2 |
+-------------------------+-----------------+-------+------+

---

使用条件聚合：

select
    title,
    writer, 
    sum(status = 'READY') ready,
    count(*) stock
from books
group by title, writer

---

sum（status='READY'）

是一个很好的MySQL快捷方式，可以计算满足内部条件的记录数（

status='READY'

）。它依赖于这样一个事实，即在数字上下文中，MySQL将真实条件评估为

1

（将错误条件评估为

0

）。

好吧，告诉我们你能做什么，让我们为你做所有的工作