Syntax error in the JOIN operation - sql

Question

I have a search button which searches in 4 tables. So I made the Sql query with three inner, and I have CheckBoxes so if the CheckBox is checked it adds the conditions to the query. But I have a problem which is:
System.Data.OleDb.OleDbException
Syntax error in the JOIN operation
cmd = New OleDbCommand(Sql, myConnection)
Dim da As OleDbDataAdapter
Dim sql = "SELECT * from (tblDopages AS A INNER JOIN tblMatrice AS B on A.strMatrice = B.strMatrice) INNER JOIN (tblRefMatrice AS C on B.strMatrice = C.strMatrice) INNER JOIN (tblRefMatDetails AS D on C.intIDref = D.intIDRef) WHERE "
If CKBrefech.Checked = True Then
sql = sql & "strRefEch = '" & TBrefech.Text & "' AND "
End If
If CKBmethode.Checked = True Then
sql = sql & "strMethode = '" & CBmethode.Text & "' AND "
End If
If CKBpurif.Checked Then
sql = sql & "strPurif = '" & CBpurif.Text & "' AND "
End If
If CKBmatrice.Checked Then
sql = sql & "strMatrice = '" & CBmatrice.Text & "' AND "
End If
If CKBmol.Checked Then
sql = sql & "strMolecule = '" & CBmol.Text & "' AND "
End If
If CKBechprep.Checked Then
sql = sql & "datDatePrepa >= #DatPrepa AND "
cmd.Parameters.Add("#DatPrepa", OleDbType.Date).Value = DTPechprep.Value.Date
End If
If CKBechau.Checked Then
sql = sql & "datDatePrepa <= #Datau AND "
cmd.Parameters.Add("#Datau", OleDbType.Date).Value = DTPechau.Value.Date
End If
If CKBtrigprepa.Checked = True Then
sql = sql & "strTrigPrepa = '" & TBtrigprepa.Text & "' AND "
End If
If CKBtriganaly.Checked = True Then
sql = sql & "strTrigAnaly = '" & TBtrigAnaly.Text & "' AND "
End If
If CKBappar.Checked = True Then
sql = sql & "strNomTech = '" & CBappar.Text & "' AND "
End If
If CKBnumappar.Checked = True Then
sql = sql & "[strEquip(Appareil)] = '" & CBnumappar.Text & "' AND "
End If
If CKBteneurmini.Checked = True Then
sql = sql & "dblDopage >= " & TBteneurmini.Text & " AND "
End If
If CKBteneurmax.Checked = True Then
sql = sql & "dblDopage <= " & TBteneurmax.Text & " AND "
End If
If GroupBox1.Enabled Then
Try
If CKBnomref.Checked Then
sql = sql & "D.strReferentiel = '" & CBnomref.Text & "' AND "
End If
If CKBniv1.Checked Then
sql = sql & "D.strNIveau1 = '" & CBniv1.Text & "' AND "
End If
If CKBniv2.Checked Then
sql = sql & "D.strNiveau2 = '" & CBniv2.Text & "' AND "
End If
If CKBniv3.Checked Then
sql = sql & "D.strNiveau3 = '" & CBniv3.Text & "' AND "
End If
If CKBniv4.Checked Then
sql = sql & "D.strNiveau4 = '" & CBniv4.Text & "' AND "
End If
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End If
If sql.EndsWith(" AND ") Then
sql = sql.Substring(0, sql.Length - 4)
End If
' Remove the WHERE if no textbox has been filled....'
If sql.EndsWith(" WHERE ") Then
sql = sql.Substring(0, sql.Length - 7)
End If
' cmd = New OleDbCommand(sql, myConnection)
cmd.CommandText = sql
cmd.Connection = myConnection
Dim MyDataSet As New DataSet
da = New OleDbDataAdapter(sql, myConnection)
da.SelectCommand = cmd
da.SelectCommand.Parameters.Add(New OleDbParameter("#DatPrepa", DTPechprep.Value)) 'adding date parameters to datatable
da.SelectCommand.Parameters.Add(New OleDbParameter("#datau", DTPechprep.Value)) 'adding date parameters to datatable
'da.SelectCommand.Parameters.Add(New OleDbParameter("#Matrice", matrice.ToString)) 'adding Matrice parameters to datatable
da.Fill(MyDataSet, "Matrice")
DataGridView1.DataSource = MyDataSet.Tables("Matrice")
'to focus on first row of DGV after populating it
DataGridView1.Rows(0).Selected = True
LBnumresult.Text = DataGridView1.RowCount - 1

Answer 1

Well you have some syntax errors. Change this:
SELECT *
FROM (tblDopages AS A
INNER JOIN tblMatrice AS B ON A.strMatrice = B.strMatrice)
INNER JOIN (tblRefMatrice AS C ON B.strMatrice = C.strMatrice)
INNER JOIN (tblRefMatDetails AS D ON C.intIDref = D.intIDRef)
WHERE strMethode = 'MarMeth1' AND strPurif = 'MarPurif2'
to this:
SELECT *
FROM ((tblDopages AS A
INNER JOIN tblMatrice AS B ON A.strMatrice = B.strMatrice)
INNER JOIN tblRefMatrice AS C ON B.strMatrice = C.strMatrice)
INNER JOIN tblRefMatDetails AS D ON C.intIDref = D.intIDRef
WHERE strMethode = 'MarMeth1' AND strPurif = 'MarPurif2'
General:
SELECT ...
FROM ((--here N-2 parentesis
table1
JOIN table2 ON ...)
JOIN table3 ON ...)
JOIN table4 ON ...)
JOIN tableN ON ...--here no parentesis

Answer 2

This is the answer I used which contains 2 inner join between 3 tables and left join.
I made first the inner join and finally the left join
Dim sql = "SELECT distinct A.* FROM ((tblMatrice AS B INNER JOIN tblRefMatrice AS C ON B.strMatrice = C.strMatrice) INNER JOIN tblRefMatDetails AS D ON C.intIDref = D.intIDRef) LEFT OUTER JOIN tblDopages AS A on A.strMatrice = B.strMatrice where "