Question

我使用的是Amazon RDS（Aurora），因此无法访问crosstab（）函数。我的数据集是每个用户的特定操作数，如下所示：

|   uid   | action1 | action2 |
| alice   | 2       | 2       |
| bob     | 1       | 2       |
| charlie | 5       | 0       |

如何透过此数据集制作动作计数直方图？所以它看起来像：

# | Action1 | Action2
---------------------
0 |         |    1
1 |   1     |    
2 |   1     |    2
3 |         |    
4 |         |    
5 |   1     |    
6 |         |

这是我已经使用已输入值的SQL小提琴：http://sqlfiddle.com/#!17/2b966/1

Answer 1

我有一个解决方案，但它非常详细：

WITH nums AS (
SELECT n
FROM (VALUES (0), (1), (2), (3), (4), (5)) nums(n)
),

action1_counts as (
  select
    action1,
    count(*) as total
  from test
  group by 1
),

action2_counts as (
  select
    action2,
    count(*) as total
  from test
  group by 1
)

select
  nums.n,
  coalesce(a1.total, 0) as Action1,
  coalesce(a2.total, 0) as Action2
from nums
LEFT join action1_counts a1 on a1.action1 = nums.n
LEFT join action2_counts a2 on a2.action2 = nums.n
order by 1

Answer 2

假设行动在0到6之间。

select a1.action, a1.action1, nullif(count(t2.action2),0) as action2
from
(  select t.action, nullif(count(t1.action1),0) as action1 
   from
   (select action from generate_series(0,6) g(action)) t
   left join
   test t1
   on t1.action1 = t.action
   group by t.action 
) a1
left join
test t2
on t2.action2 = a1.action
group by a1.action, a1.action1
order by a1.action

如何围绕值转换postgresql（Amazon RDS）数据集以制作直方图？

2 个答案: