Records becomes repetitive in vb.net - sql-server

Question

I have relational database. Each students has different history(one to many). The data is correct but the problem here is that student information become repetitive when loading in datagridview.I use DISTINCT function but it does not work. Can someone help me to figure out what's wrong with my code.
vb.net code when load
Using cmd As New SqlClient.SqlCommand("dbo.uspSELECTALL", cn)
da.SelectCommand = cmd
dt.Clear()
da.Fill(dt)
dgv1.RowTemplate.Height = 50
dgv1.DataSource = dt
For i As Integer = 0 To dgv1.Columns.Count - 1
If TypeOf dgv1.Columns(i) Is DataGridViewImageColumn Then
DirectCast(dgv1.Columns(i), DataGridViewImageColumn).ImageLayout = DataGridViewImageCellLayout.Stretch
End If
Next
End Using
stored procedure code
ALTER PROCEDURE [dbo].[uspSELECTALL]
AS
BEGIN
SET NOCOUNT ON;
SELECT DISTINCT SI.StudentID,SI.Surname,SI.FirstName,SI.MiddleName, SI.StudAddress ,
SI.BirthDay,SI.Gender, SI.Nationality, SI.BirthPlace,
SI.TelNum,SI.SchoolWhereGraduated ,
SI.DatesWhenGraduated, SI.SchoolLastAttended,
SI.Note,SI.StudImage,
PI.Father_FirstName,PI.Father_LastName,
PI.Father_MI,PI.Father_Occupation,
PI.Father_TelNUm, PI.Mother_FirstName, PI.Mother_LastName,
PI.Mother_MI,PI.Mother_Occupation,PI.Mother_TelNum,
PI.Contact_FirstName,PI.Contact_LastName,PI.Contact_MI,
PI.Contact_Mobile,PI.Contact_TelNum,PI.Contact_Address,
SH.SchoolYear,SH.Levels,SH.Section,SH.DateEnrolled
FROM StudentInformation SI
JOIN StudentHistory SH
ON SI.StudentID = SH.StudentID
JOIN ParentInformation PI
ON PI.ParentID = SI.ParentID
END

Answer 1

If you want show in the DataGridView only distincts id's of students,
then you need use another query.
Your current query always return multiply rows per student if student have more then one history.
One approach will be removing all columns of table StudentHistory from SELECT statement and keep DISTINCTkeyword in the query.
SELECT DISTINCT SI.StudentID,SI.Surname,SI.FirstName,SI.MiddleName, SI.StudAddress ,
SI.BirthDay,SI.Gender, SI.Nationality, SI.BirthPlace,
SI.TelNum,SI.SchoolWhereGraduated ,
SI.DatesWhenGraduated, SI.SchoolLastAttended,
SI.Note,SI.StudImage,
PI.Father_FirstName,PI.Father_LastName,
PI.Father_MI,PI.Father_Occupation,
PI.Father_TelNUm, PI.Mother_FirstName, PI.Mother_LastName,
PI.Mother_MI,PI.Mother_Occupation,PI.Mother_TelNum,
PI.Contact_FirstName,PI.Contact_LastName,PI.Contact_MI,
PI.Contact_Mobile,PI.Contact_TelNum,PI.Contact_Address
FROM StudentInformation SI
JOIN StudentHistory SH
ON SI.StudentID = SH.StudentID
JOIN ParentInformation PI
ON PI.ParentID = SI.ParentID
Another way will be filter DataTable which was filled by your query.
Using cmd As New SqlClient.SqlCommand("dbo.uspSELECTALL", cn)
da.SelectCommand = cmd
dt.Clear()
da.Fill(dt)
dgv1.RowTemplate.Height = 50
'Filtering for distinct rows
Dim view As New DataView(GetData())
Dim distinctColumnNames As String() =
{
"StudentID", "Surname", "FirstName", "MiddleName",
"StudAddress" ' and so on
}
Dim distinctValues As DataTable = view.ToTable(True, distinctColumnNames)
dgv1.DataSource = distinctValues
'Your other code
End Using
view.ToTable(True, distinctColumnNames) if first parameter is True then only distinct rows, based on columnnames will be included