如何在 MS Access 中填充字段描述

Question

当通过 ODBC（尤其是 AS/400）链接到外部数据源时，我经常在另一端遇到神秘的字段名称，而数据字典不可用。在极少数情况下，我能够从另一个数据库中获取字段描述，我希望能够一次将它们全部导入，而不是一次将每个描述复制/粘贴到表格设计表单中。

我无法在系统表中找到这个，所以我不知道这个元数据存储在哪里。关于它在哪里以及是否可以批量更新的任何想法？

更新：我设法使用 OpenSchema 方法读取了架构（参见下面的代码），但这会返回一个只读数据集，使我无法更新描述。

Function UpdateFieldDescriptions()
Dim cn As New ADODB.Connection
Dim rs As ADODB.Recordset
Dim rs2 As Recordset
Dim strSQL As String
Dim strDesc As String

Set cn = CurrentProject.Connection
Set rs = cn.OpenSchema(adSchemaColumns)

While Not rs.EOF
    If Left(rs!table_name, 4) <> "MSys" Then
        Debug.Print rs!table_name, rs!column_name, rs!Description
        strSQL = "SELECT Description " & _
            "FROM tblColumnDescriptions a " & _
            "WHERE a.Name = """ & rs!table_name & """ AND " & _
            "a.Column = """ & rs!column_name & """;"
        Set rs2 = CurrentDb.OpenRecordset(strSQL)
        While Not rs2.EOF
            strDesc = rs2.Fields(0)
            rs!Description = strDesc ' <---This generates an error
        Wend
    End If
    rs.MoveNext
Wend

rs.Update
rs.Close
Set rs = Nothing
Set rs2 = Nothing
Set cn = Nothing

End Function

Answer 1

使用 DAO 代替 ADO：

Sub SetFieldDesc(TblName As String, FldName As String, Description As String)
Dim db As DAO.Database, td As DAO.TableDef, fld As DAO.Field

    Set db = CurrentDb()
    Set td = db.TableDefs(TblName)
    Set fld = td.Fields(FldName)

    On Error Resume Next
    fld.Properties("Description") = Description
    If Err.Number = 3270 Then 'Property not found.'
        fld.Properties.Append fld.CreateProperty("Description", dbText, Description)
    End If
End Sub

Answer 2

一些可能会有所帮助的注释。下面显示了来自 adSchemaColumns 的字段描述。

   Function ListFieldDescriptions()
   ''List field descriptions
   Dim cn As New ADODB.Connection, cn2 As New ADODB.Connection
   Dim rs As ADODB.Recordset, rs2 As ADODB.Recordset

       Set cn = CurrentProject.Connection

       Set rs = cn.OpenSchema(adSchemaTables, _
           Array(Empty, Empty, Empty, "tablenamehere"))

       While Not rs.EOF
           Debug.Print rs!table_name; "   desc=  "; rs!Description
           Set rs2 = cn.OpenSchema(adSchemaColumns, _
               Array(Empty, Empty, "" & rs!table_name & ""))
           While Not rs2.EOF
               Debug.Print "     " & rs2!Column_Name
               Debug.Print "     " & rs2!Data_Type
               Debug.Print "     " & rs2!Description
               Debug.Print "     " & rs2!Is_Nullable
               rs2.MoveNext
           Wend
       rs.MoveNext
       Wend
       rs.Close
       Set cn = Nothing

   End Function    

发件人：http://wiki.lessthandot.com/index.php/ADO_Schemas