聚合行以根据 MySQL 中的行内容创建新列

Question

I currently have a query that returns this result:

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

And I would like to be able to convert it into a descriptive table like this.

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

Is there some kind of rollup or handy function that lets me aggregate rows like this?

Answer 1

You want to pivot the data. I would recommend conditional aggregation:

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

In redshift and postgresql one should use

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;