如何在範圍內顯示數據？

Question

我想從數據庫中獲取的數據顯示，因爲這

Total_marks | No of Students 

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

的樣本數據：

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 

但我剛剛得到的列標題，並沒有數據。如何正確制定查詢。此外，我希望這將顯示爲在ASP.NET中的圖表。其中，代碼如下：

{ 
    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獲得間隔，然後GROUP BY相同的時間間隔來獲得學生的數量，其落在各個區間。

檢查該查詢，並希望它可以幫助你

更改：使用表變量來存儲間隔的列表，然後用連接來獲得所需的輸出。

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

嘗試這個

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