如何在范围内显示数据？

Question

我想从数据库中获取的数据显示，因为这

Total_marks | No of Students 

10-20  | 2 
20-30  | 1 
30-40  | 3 
so on 

的样本数据：

barcode(student id) | Total_marks                     
    200056 | 70 
    200071 | 51 
    200086 | 40 
    200301 | 56 
    200317 | 73 
    200316 | 35 
    200217 | 42 
    200104 | 80 
    200015 | 63 

我想：

 SELECT 
count(*) as no_of_students, 
CASE 
    WHEN Total_marks BETWEEN 10 and 20 THEN '1' 
    WHEN Total_marks BETWEEN 20 and 30 THEN '2' 
    WHEN Total_marks BETWEEN 30 and 40 THEN '3' 
    WHEN Total_marks BETWEEN 40 and 50 THEN '4' 
    WHEN Total_marks BETWEEN 50 and 60 THEN '5' 
    WHEN Total_marks BETWEEN 60 and 70 THEN '6' 
    WHEN Total_marks BETWEEN 70 and 80 THEN '7' 
    WHEN Total_marks BETWEEN 80 and 90 THEN '8' 
    WHEN Total_marks BETWEEN 90 and 100 THEN '9' 
END AS intervals 
FROM 
[database] 
WHERE 
0 - 10 = '0' and 10 - 20 = '1' and 20 - 30 = '2' and 30 - 40 = '3' and 40 -  50 = '4' and 50 - 60 = '5' and 60 - 70 = '6' and 70 -80 = '7' and 80 - 90 = '8' and 90 - 100 = '9' GROUP BY Total_marks 

但我刚刚得到的列标题，并没有数据。如何正确制定查询。此外，我希望这将显示为在ASP.NET中的图表。其中，代码如下：

{ 
    connection.Open(); 
      SqlCommand cmd = new SqlCommand("Query", connection); 
      cmd.ExecuteNonQuery(); 


      SqlDataAdapter da = new SqlDataAdapter(cmd); 
      DataSet ds = new DataSet(); 
      da.Fill(ds); 

      DataTable ChartData = ds.Tables[0]; 

       //storing total rows count to loop on each Record 
      string[] XPointMember = new string[ChartData.Rows.Count]; 
      Chart1.ChartAreas[0].AxisX.IsStartedFromZero = true; 

      decimal[] YPointMember = new decimal[ChartData.Rows.Count]; 

      int totalrows = ChartData.Rows.Count; 

      if (totalrows > 0) 
      { 
       for (int count = 0; count < ChartData.Rows.Count; count++) 
       { 
        //storing Values for X axis 
        XPointMember[count] = ChartData.Rows[count]["Number_of_students"].ToString(); 

        //storing values for Y Axis 
        YPointMember[count] = Convert.ToDecimal(ChartData.Rows[count]["Total_accumulated_score_achieved" + "%"]); 

        connection.Close(); 
    } 

Answer 1

您需要使用CASE获得间隔，然后GROUP BY相同的时间间隔来获得学生的数量，其落在各个区间。

检查该查询，并希望它可以帮助你

更改：使用表变量来存储间隔的列表，然后用连接来获得所需的输出。

Declare @Intervals table (Interval varchar(10)) 
Insert into @Intervals values('10-20'),('21-30'),('31-40'),('41-50'),('51-60'),('61-70'),('71-80'),('81-90'),('91-100') 

SELECT i.Interval as [Intervals], ISNULL(count(t.Intervals),0) as [NoOfStudents] 
FROM (
    SELECT CASE 
    WHEN Total_marks BETWEEN 10 and 20 THEN '10-20' 
    WHEN Total_marks BETWEEN 21 and 30 THEN '21-30' 
    WHEN Total_marks BETWEEN 31 and 40 THEN '31-40' 
    WHEN Total_marks BETWEEN 41 and 50 THEN '41-50' 
    WHEN Total_marks BETWEEN 51 and 60 THEN '51-60' 
    WHEN Total_marks BETWEEN 61 and 70 THEN '61-70' 
    WHEN Total_marks BETWEEN 71 and 80 THEN '71-80' 
    WHEN Total_marks BETWEEN 81 and 90 THEN '81-90' 
    WHEN Total_marks BETWEEN 91 and 100 THEN '91-100' 
    end as Intervals 
    from @yourtable) t 
    right join @Intervals i on i.Interval = t.Intervals 
group by i.Interval 

Answer 2

尝试这个

create table StudentData 
(
    StudentID INT, 
    Total_Marks INT 
) 

insert into StudentData values(1,10) 
insert into StudentData values(2,30) 
insert into StudentData values(3,10) 
insert into StudentData values(4,50) 
insert into StudentData values(5,50) 
insert into StudentData values(6,70) 
insert into StudentData values(7,80) 
insert into StudentData values(8,70) 
insert into StudentData values(9,80) 
insert into StudentData values(10,80) 
insert into StudentData values(11,90) 
insert into StudentData values(12,100) 
insert into StudentData values(13,40) 

SELECT t.Intervals as [Intervals], count(*) as [NoOfStudents] 
FROM (
SELECT CASE 
WHEN Total_marks BETWEEN 10 and 20 THEN '10-20' 
WHEN Total_marks BETWEEN 20 and 30 THEN '20-30' 
WHEN Total_marks BETWEEN 30 and 40 THEN '30-40' 
WHEN Total_marks BETWEEN 40 and 50 THEN '40-50' 
WHEN Total_marks BETWEEN 50 and 60 THEN '50-60' 
WHEN Total_marks BETWEEN 60 and 70 THEN '60-70' 
WHEN Total_marks BETWEEN 70 and 80 THEN '70-80' 
WHEN Total_marks BETWEEN 80 and 90 THEN '80-90' 
WHEN Total_marks BETWEEN 90 and 100 THEN '90-100' 
end as Intervals 
from StudentData) t 
group by t.Intervals 

Output: 

Intervals NoOfStudents 
    10-20  2 
    20-30  1 
    30-40  1 
    40-50  2 
    60-70  2 
    70-80  3 
    80-90  1 
    90-100  1