Question

我有这样的查询：

select to_date(to_char(registime, 'YYYY-MM'),'YYYY-MM') as dt,count(id) as total_call  
from all_info 
where alarm_id is null
group by dt   
order by dt

结果就像这样：

dt          total_call      
2011-03-01     45
2011-04-01     61
2011-05-01     62
2011-06-01     41
2011-07-01     48
2011-08-01     42
2011-09-01     28
2011-10-01     39

我希望结果如下面的演示，表格形式：

2011-03-01   2011-04-01  2011-05-01  2011-06-01  ..........
   45            61          62          41

我想使用交叉表，但它似乎不起作用？

Answer 1

查看contrib模块 tablefunc 。它提供了您正在寻找的枢轴表功能。请参阅manual here。

关注installation instructions here或@Paul Tomblin在上述评论中提出的文章。

然后你的功能看起来像这样：

SELECT *
  FROM crosstab($$
SELECT 'total_calls'::text AS col_name
      ,to_char(registime, '"x"YYYY_MM_01') as dt
      ,count(id) as total_call  
FROM   all_info 
WHERE  alarm_id is null
GROUP  BY dt   
ORDER  BY dt
$$)
AS ct(
 call_day text
,x2011_03_01 int8
,x2011_04_01 int8
,x2011_05_01 int8
,x2011_06_01 int8
,x2011_07_01 int8
,x2011_08_01 int8
,x2011_09_01 int8
,x2011_10_01 int8);

输出：

  call_day   | x2011_03_01 | x2011_04_01 | x2011_05_01 | x2011_06_01 | x2011_07_01 | x2011_08_01 | x2011_09_01 | x2011_10_01
-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------
 total_calls |           1 |           4 |           4 |           2 |           1 |           5 |           1 |           1

列名不能以数字开头（或者你必须双引号），这就是我用x作为日期前缀的原因。我也简化了你的查询您可以将其包装在视图或功能中以供重复使用也许是一个plpgsql函数，可以动态调整列名和EXECUTE。

More details, explanation and links in this related answer

在PostgreSQL中显示一行中的多个列值

1 个答案: