聚合行以基于MySQL中的行内容创建新列

Question

我目前有一个返回此结果的查询：

|product|status|
|-------|------|
|string1|A     |
|string1|C     |
|string2|B     |
|string2|A     |
|string3|B     |
|string3|B     |
----------------

我希望能够将其转换为这样的描述性表格。

|product|total |A    |B    |C     |
|-------|------|-----|-----|------|
|string1|2     |1    |0    |1     |
|string2|2     |1    |1    |0     |
|string3|2     |0    |2    |0     |
-----------------------------------

是否有某种汇总或方便的功能让我汇总这样的行？

Answer 1

您想要转动数据。我建议使用条件聚合：

select product, count(*) as total,
       sum( status = 'A' ) as A,
       sum( status = 'B' ) as B,
       sum( status = 'C' ) as C
from (<your query here>) q
group by product;

Answer 2

在redshift和postgresql中，应该使用

select product, count(*) as total,
       count(CASE WHEN status = 'A' THEN 1 END) as A,
       count(CASE WHEN status = 'B' THEN 1 END) as B,
       count(CASE WHEN status = 'C' THEN 1 END) as C
from (<your query here>) q
group by product;