SQL结果按月分组

Question

我正在尝试返回一些在滚动12个月内分散的结果，例如：

MONTH       IN   OUT
January    210    191
February   200    111
March      132    141
April      112    141
May        191    188 
etc...

如何在日期范围内分散结果，并在第一列中填充月份名称？

在MSSQL中，它将类似于：

SELECT  COUNT(problem.problem_type = 'IN') AS IN, 
    COUNT(problem.problem_type = 'OUT') AS OUT, 
    DATEPART(year, DateTime) as Year,
    DATEPART(month, DateTime) as Month
FROM problem
WHERE   (DateTime >= dbo.FormatDateTime('2010-01-01')) 
    AND 
    (DateTime < dbo.FormatDateTime('2010-01-31'))
GROUP BY DATEPART(year, DateTime),
    DATEPART(month, DateTime);

但这是针对Oracle数据库的，因此DATEPART和DateTime不可用。

我的问题表大致为：

problem_ID Problem_type   IN_Date                     OUT_Date
   1           IN        2010-01-23 16:34:29.0       2010-02-29 13:06:28.0
   2           IN        2010-01-27 12:34:29.0       2010-01-29 12:01:28.0
   3           OUT       2010-02-13 13:24:29.0       2010-09-29 15:04:28.0
   4           OUT       2010-02-15 16:31:29.0       2010-07-29 11:03:28.0

Answer 1

使用：

  SELECT SUM(CASE WHEN p.problem_type = 'IN' THEN 1 ELSE 0 END) AS IN, 
         SUM(CASE WHEN p.problem_type = 'OUT' THEN 1 ELSE 0 END) AS OUT, 
         TO_CHAR(datetime, 'YYYY') AS year,
         TO_CHAR(datetime, 'MM') AS month
    FROM PROBLEM p
   WHERE p.DateTime >= TO_DATE('2010-01-01', 'YYYY-MM-DD') 
     AND p.DateTime < TO_DATE('2010-01-31', 'YYYY-MM-DD') 
GROUP BY TO_CHAR(datetime, 'YYYY'), TO_CHAR(datetime, 'MM')

您还可以使用：

  SELECT SUM(CASE WHEN p.problem_type = 'IN' THEN 1 ELSE 0 END) AS IN, 
         SUM(CASE WHEN p.problem_type = 'OUT' THEN 1 ELSE 0 END) AS OUT, 
         TO_CHAR(datetime, 'MM-YYYY') AS mon_year
    FROM PROBLEM p
   WHERE p.DateTime >= TO_DATE('2010-01-01', 'YYYY-MM-DD') 
     AND p.DateTime < TO_DATE('2010-01-31', 'YYYY-MM-DD') 
GROUP BY TO_CHAR(datetime, 'MM-YYYY')