如何在 sql 上 select 直方图？

Question

我有以下 table messages:

destination_number | message_text | pk/sender_number/metadata/timestamps/other_stuff
123                | hi           | ...
456                | at 4         | ...
123                | how are you? | ...
123                | I'm David    | ...
456                | please       | ...
789                | no           | ...
789                | stop         | ...
012                | exit         | ...

做 select count(1) as quantity, destination_number from messages group by destination_number 我得到：

quantity | destination_number
3        | 123
2        | 456
2        | 789
1        | 012

现在我想要一个直方图：

quantity | quantity_of_numbers_that_received_that_quantity
3        | 1                      // only number 123 received 3 messages
2        | 2                      // numbers 456 and 789 received 2 messages
1        | 1                      // only 012 received 1 message

我的问题是：什么查询会直接从 messages 带来最后一个 table？

Answer 1

select quantity, count(destination_number) as quantity_of_numbers_that_received_that_quantity
from (
  select count(1) as quantity, destination_number 
  from messages 
  group by destination_number
)
group by quantity

Answer 2

如果我没理解错，请使用二级聚合：

select quantity, count(*)
from (select count(1) as quantity, destination_number
      from messages
      group by destination_number
     ) m
group by quantity
order by quantity;

我通常会包含类似 min(destination_number), max(destination_number) 的内容来查看示例值。