如何按范围显示数据？

Question

我希望从数据库中获取的数据显示为这样

Total_marks | No of Students

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

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

我试过了：

     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

但我只得到列标题而没有数据。如何正确制定查询。我还希望它在 ASP.NET 中显示为图表。代码在哪里：

    {
    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

试试这个

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

Answer 2

您需要使用CASE 来获取区间，然后使用GROUP BY 相同的区间来获取落在各个区间内的学生人数。

检查此查询，希望对您有所帮助

更改：使用表变量来存储间隔列表，然后使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