[Student] Error Collection

    Students basically almost the same tune, I found I had a lot of mistakes, here to do some summary.

1.3021

I encountered this error is almost the most mistakes, as long as there is no data, it will pop out this error. Ah, see? I point out this sentence crux of this error is that there is no data, the database can not find data, the so-called "original aim," Just know this, we can quickly resolve this error.

---

Where students, often where this error happen?

1. 

   When ordered to modify student information form, but there is also no student information database, the error appeared, or you will delete all the records,

2. 

   Well, how do we deal with it?

   ---

    Dim mrc As ADODB.Recordset
       Dim txtsql As String
       Dim msgtext As String
       
       txtsql = "select * from class_Info "
       Set mrc = ExecuteSQL(txtsql, msgtext)
       If mrc.EOF And mrc.BOF Then
           MsgBox "没有数据，请添加！", 0 + 48, 提示
           frmaddclassinfo.Show
           Exit Sub
       Else
           frmmodifyclassinfo.Show
       End If

    

I almost eat around the world use this code, as long as I appeared 3021, my first thought would be solved with this code.

Second: When data is deleted, delete records more than two error does not appear, but the error will occur when deleting the last record.   
Act 1, the use of error-handling statement (premise: While click the Delete button after an error, but re-open the record has been deleted) 
 

 

On Error GoTo 1

 1:
    the If Err = 3021 the Then
        MsgBox "has no data, add data", vbOKOnly + vbExclamation, "prompt"
        Unload Me
        frmaddclassinfo.Show
    End the If
    Else
      mrc.Bookmark = MyBookmark
      Call ViewData
    End the If

Act 2, written judgment statement to determine whether the last record
 

 Private Sub deleteCommand_Click()   

= mrc.Bookmark MyBookmark   
    str2 $ = MsgBox ( "Delete this record?", vbOKCancel, "delete the current record.")   

VbOK the Then str2 = $ IF mrc.MoveNext       
                  'determines whether the last record   

If mrc.EOF Then

   mrc.MovePrevious

If mrc.BOF Then 'If so, then deleted, to avoid the implementation of the statement call viewdata

     mrc.MoveNext

     mrc.Delete

     Msgbox "record is already empty," vbokonly + vbexclamation, "Warning"

     unload me  

else

     mrc.movefirst

     mybookmark=mrc.bookmark

     mrc.movelast

      mrc.delete

      mrc.bookmark=mybookmark   

      mrc.close

2.91

 I already heard this mistake, and sure enough, I met this error and whether they most careful about, such as the SQL statement quotes are not complete, the SQL statement is wrong, more space, less space, will appear this error.

I'm wrong here, because I write the SQL statement is incomplete, the right should be

txtSQL = "select * from student_Info where student_ID = '" & comboSID.Text & "'"

3.3265

This error is not common,

 But, here I am wrong, careful not entirely their own, how can the information appears in the Add-grade grade grade information in the form of it. Deleted it.

4. cross-border issues

When you enter data exceeds the range or greater than the desired database, for example, string is limited to 11 digits into the case 10, the error occurs.