Question

我的表格与下面的内容完全相同

School              Course              Date             Status

SCH1            SCH1CRS1        2011-01-15           S

                SCH1CRS1        2011-01-17           C

SCH1            SCH1CRS2        2011-01-15           S

SCH2            SCH2CRS1        2011-01-15           S

                SCH2CRS1        2011-01-21           C

SCH2             SCH2CRS2        2011-01-22          S

               SCH2CRS2          2011-01-25          C

状态S =已开始且C =已完成，日期为开始日期和完成日期。当课程开始时，用户输入schoolID，courseID，日期和状态，但是当课程完成后，用户输入courseID，日期和状态。用户不输入SchoolID。从表中我们可以理解SCH1CRS1和SCH1CRS2属于SCH1。我需要知道的是，在某个特定的学校，在特定的日期，有多少课程已经开始但尚未完成。

您可以在SCH1中看到，2011-01-15已经开始了两个课程，但只有一个课程已经完成。课程何时完成并不重要。我需要知道的是否已经完成。在SCH2中，两门课程在不同的日期开始，但都已完成。

结果表应该是这样的

Input Date: 2011-01-15

School             Not completed  

SCH1                       1

SCH2                       0

Input Date: 2011-01-22

School           Not Completed

SCH2                      0

我认为这是一个混乱的表，并没有遵循数据库设计规则。但这就是我所拥有的。没有选择。

由于

Answer 1

您必须找到与已开始课程相关的已完成课程，如果没有完成课程，请计1。

SELECT startedCourse.School AS School, 
       SUM(CASE WHEN completedCourse IS NULL THEN 1 ELSE 0 END) AS NotCompleted
FROM MyTable startedCourse
    LEFT OUTER JOIN MyTable completedCourse
        ON startedCourse.Status = 'S'
        AND completedCourse.Status = 'C'
        AND startedCourse.Course = completedCourse.Course
WHERE startedCourse.Date = ?
GROUP BY startedCourse.School

Answer 2

从头顶开始：

select c_started.courseID, c_started.courseDate as StartDate, c_completed.courseDate as CompletedDate, 
case 
 when c_completed.courseDate IS NULL then 'incomplete'
 Else 'completed'
end as courseStatus
from tbCourses as c_started
left join tbCourses as c_completed on c_started.courseID = c_completed.courseID 
and c_started.courseDate < c_completed.courseDate
where c_started.Status = 'S'

会给你以下内容：

courseID - StartDate - CompletedDate - courseStatus

course1 - 2010-01-12 - 2010-02-25 - 已完成

course2 - 2011-01-21 - NULL - 不完整

course3 - 2010-10-15 - NULL - 不完整

Answer 3

这个怎么样：

declare @InputDate datetime = '20110115';

with cCourseList as (

select  t1.School, t1.Course, DateStarted = t1.Date,
        t2.DateCompleted
from    tbl t1
outer apply 
        (select  top(1) DateCompleted = t2.Date
        from    tbl t2
        where   t2.Course = t1.Course
            and t2.Status = 'C'
        order by t2.Date) t2
where   t1.Status = 'S'

)

select  cl.School, 
        [Not Completed] = sum(case when cl.DateCompleted is null then 1 else 0 end)
from    cCourseList cl
where   cl.DateStarted <= @InputDate
group by cl.School;

在sql server中构建sql查询的困惑

3 个答案: