Question

我有下表：

ID    Day    Count
1      '1'     1
1      '2'     2
1      '2'     7
2      '2'     4
2      '2'     3

我正在做以下查询：

select ID, Day, sum(Count) from test_table group by ID, Day

我得到下表：

ID    Day    Count
1      '1'     1
1      '2'     9
2      '2'     7

我想要的是

ID    Day1    Day2
1      1       9
2      0       7

我该怎么做？

Answer 1

我只会使用条件聚合：

select ID, 
       sum(case when day = 1 then count else 0 end) as day_1,
       sum(case when day = 2 then count else 0 end) as day_2
from test_table
group by ID;

Answer 2

使用tablefunc module中的crosstab()。

这样的事情：

SELECT *
FROM crosstab(
  $$select ID, Day, sum(Count)
   from foo2
   where Day = '1' or Day = '2'
   group by ID, Day
   order by 1,2$$)
AS ct(ID int, day_1 BIGINT, day_2 BIGINT);

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2 个答案: