ACC2000: "Too Many Fields Defined" Error Message in Update Query

When you run an update query with more than 127 fields selected, you may receive the error message: However, this same query will run correctly when you select 127 fields or fewer.

The Microsoft Jet database engine has an internal limit of 255 fields per query. As the Microsoft Jet database engine iterates through the records in an update query, it creates a field for the original value and a field for the updated value. When more than 127 fields are selected, it reaches the 255 field limit of a query.

Consider the following SQL for an update query: Internally the query looks as follows:

• Break down the update query into multiple update queries with 127 or fewer fields per query.
  
  -or-
  
  
• Update the fields by using a recordset in Visual Basic for Applications.
  

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Steps to Reproduce Behavior

The following steps create three functions. The first function creates a table with 128 fields. The second function adds one record to the table and sets the value of the fields in that record to the word "TEXT." The third function creates an update query that updates the value in the fields to the letter "T." Run the three functions from the Immediate window and observe the error message.

1. Create the following code to create a new table, to add a record to the table, and to create an update query:

   ' ****************************************************************
   ' Declarations section of the module
   ' ****************************************************************
   
   Option Compare Database
   Option Explicit
   
   ' ****************************************************************
   ' The Fill_Table() function creates a table in the current database
   ' named Field Test with 128 fields, each of which has a Text data
   ' type and a size of five characters.
   ' ****************************************************************
   
   Function Fill_Table()
      Dim mydb As DAO.Database
      Dim tbl As DAO.TableDef
      Dim fld As DAO.Field
      Dim i As Integer
      Set mydb = CurrentDb()
      Set tbl = mydb.CreateTableDef("Field Test")
      For i = 0 To 127
        Set fld = tbl.CreateField("Field" & CStr(i + 1))
        fld.Type = DB_TEXT
        fld.Size = 5
        tbl.Fields.Append fld
      Next i
      mydb.TableDefs.Append tbl
   End Function
   
   ' ****************************************************************
   ' The Fill_Data() function adds one record to the table with
   ' all fields equal to "Text."
   ' ****************************************************************
   
   Function Fill_Data()
      Dim mydb As DAO.Database
      Dim fld As DAO.Field
      Dim rs As DAO.Recordset
      Dim i As Integer
      Set mydb = CurrentDb()
      Set rs = mydb.OpenRecordset("Field Test")
      rs.AddNew
      For i = 0 To rs.Fields.Count - 1
         rs.Fields(i).Value = "Text"
      Next i
      rs.Update
      rs.Close
   End Function
   
   ' ****************************************************************
   ' The Build_SQL() function creates an update query in the current
   ' database named Update Test which will update the 128 fields in
   ' the Field Test table to the letter 'T.'
   ' ****************************************************************
   
   Function Build_SQL()
      Dim mydb As DAO.Database
      Dim qdf As DAO.QueryDef
      Dim x As String
      Dim i As Integer
      x = "Update [Field Test] SET "
      For i = 0 To 127
         x = x + "[Field Test].Field" & CStr(i + 1) & " = 'T', "
      Next
      x = Left(x, Len(x) - 2)
      Set mydb = CurrentDb()
      Set qdf = mydb.CreateQueryDef("UpdateTest", x)
   End Function
   					

2. To run each function, type the following lines in the Immediate window. Press ENTER after each line.

   ? Fill_Table()
   ? Fill_Data()
   ? Build_SQL()
   					

3. On the File menu, click Close and Return to Microsoft Access.
4. Run the UpdateTest query.

For more information about updating recordsets, in the Visual Basic Editor, click Microsoft Visual Basic Help on the Help menu, type Update method (DAO) in the Office Assistant or the Answer Wizard, and then click Search to view the topic.

For more information about the "Too many fields defined" error message, please see the following article in the Microsoft Knowledge Base: