帮我解释一下这段代码
Private Sub ListKm()Set Rst1 = New Recordset
sql = "select * from 学科表 order by 序号"
Rst1.Open sql, db, 1, 3
If Rst1.EOF Then
GridDW.Clear
GridDW.Rows = 1
GridDW.FormatString = "^ 序号|^ 学科 |^ 总分 |^ 差生分 |^ 及格分 |^ 优秀分|^ 尖子分 "
Exit Sub
Else
Rst1.MoveLast
Rst1.MoveFirst
End If
GridDW.Clear
GridDW.Rows = 1
GridDW.FormatString = "^ 序号|^ 学科 |^ 总分 |^ 差生分 |^ 及格分 |^ 优秀分|^ 尖子分 "
Do While Not Rst1.EOF
GridDW.Rows = GridDW.Rows + 1
GridDW.TextMatrix(GridDW.Rows - 1, 0) = Rst1.Fields(0)
GridDW.TextMatrix(GridDW.Rows - 1, 1) = Rst1.Fields(1)
GridDW.TextMatrix(GridDW.Rows - 1, 2) = Rst1.Fields(2)
GridDW.TextMatrix(GridDW.Rows - 1, 3) = Rst1.Fields(3)
GridDW.TextMatrix(GridDW.Rows - 1, 4) = Rst1.Fields(4)
GridDW.TextMatrix(GridDW.Rows - 1, 5) = Rst1.Fields(5)
GridDW.TextMatrix(GridDW.Rows - 1, 6) = Rst1.Fields(6)
Rst1.MoveNext
Loop
End Sub