Question

我有一张桌子，我可以在其中找到完成课程（每门课程）平均需要多长时间

StudentName |课程| TimetoCompleteCourse

约翰尼|法语| 2
肖恩|英语| 3
芭芭拉|法语| 8个

现在我要对此进行分类：

课程|平均TimeToComplete |分类

法语| 4 | 2-4个月
英语| 3 | 1-3个月

如您所见，我想在三个月内对它们进行分类。我知道使用Case语句，但我觉得这可以通过使用mod 3或其他东西更聪明地处理...

任何想法/建议？

这就是我现在所拥有的

        Category = CASE
            WHEN avg(TimeToCompleteCourse) <=3 THEN '1-3 months'
            WHEN avg(TimeToCompleteCourse) >=4 AND avg(TimeToCompleteCourse) <=6  THEN '4-6 months'
            WHEN avg(TimeToCompleteCourse) >=7 AND avg(TimeToCompleteCourse) <=9  THEN '7-9 months'
            WHEN avg(TimeToCompleteCourse) >=10 AND avg(TimeToCompleteCourse) <=12  THEN '10-12 months'
            WHEN avg(TimeToCompleteCourse) >=13 AND avg(TimeToCompleteCourse) <=15  THEN '13-15 months'
            WHEN avg(TimeToCompleteCourse) >=16 AND avg(TimeToCompleteCourse) <=18  THEN '16-18 months'
            WHEN avg(TimeToCompleteCourse) >=19 AND avg(TimeToCompleteCourse) <=21  THEN '18-21 months'
            WHEN avg(TimeToCompleteCourse) >=22 AND avg(TimeToCompleteCourse) <=24  THEN '22-24 months'
            WHEN avg(TimeToCompleteCourse) >=25 AND avg(TimeToCompleteCourse) <=27  THEN '25-27 months'
            WHEN avg(TimeToCompleteCourse) >=28   THEN 'Way too long!'
        END

Answer 1

在我看来，你不需要模数运算符。 mod运算符将从整数除法返回余数（11 mod 3 = 2）。相反，我认为你想要舍入到最近的3个月间隔。更具体地说，取平均持续时间并将其四舍五入到最接近的3。

试试这个：

Select  Course,
        Avg(TimeToCompleteCourse) As AvgTimeToComplete,
        Convert(VarChar(4), Ceiling(Avg(TimeToCompleteCourse) / 3.0) * 3 - 2)
        + ' - ' +
        Convert(VarChar(4), Ceiling(Avg(TimeToCompleteCourse) / 3.0) * 3)
        + ' Months' As Category
From    YourTableName
Group By Course

请注意，我重复计算，其中一个上面有-2。这只是为了显示值的范围。

Answer 2

这（虽然丑陋）应该为所有模数值做技巧：

select 
course
,CASE WHEN AVG(timetocompletecourse) > 27 THEN 'Way too long'
        WHEN AVG(timetocompletecourse) < 4 THEN '1-3 Months'
        WHEN AVG(timetocompletecourse)%3 = 0 THEN CAST(AVG(timetocompletecourse)-2 AS VARCHAR(2)) + '-' + CAST(AVG(timetocompletecourse) AS VARCHAR(2)) + ' Months'
        WHEN AVG(timetocompletecourse)%3 = 1 THEN CAST(AVG(timetocompletecourse) AS VARCHAR(2)) + '-' + CAST(AVG(timetocompletecourse)+2 AS VARCHAR(2)) + ' Months'
        WHEN AVG(timetocompletecourse)%3 = 2 THEN CAST(AVG(timetocompletecourse)-1 AS VARCHAR(2)) + '-' + CAST(AVG(timetocompletecourse)+1 AS VARCHAR(2)) + ' Months'
        END as rangename
FROM yourtable
GROUP BY 
course

用模数来计算周期？

2 个答案: