Microsoft KB Archive/199076

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

Article ID: 199076

Article Last Modified on 6/23/2005

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APPLIES TO


 * Microsoft Access 2000 Standard Edition

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This article was previously published under Q199076



Moderate: Requires basic macro, coding, and interoperability skills.

This article applies only to a Microsoft Access database (.mdb).



SYMPTOMS
When you run an update query with more than 127 fields selected, you may receive the error message:

Too many fields defined.

However, this same query will run correctly when you select 127 fields or fewer.



CAUSE
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:

UPDATE Table SET A=B, C=D

Internally the query looks as follows:

SELECT A,B,C,D

FROM Table



RESOLUTION

 * 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.



MORE INFORMATION
Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements.

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.   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   To run each function, type the following lines in the Immediate window. Press ENTER after each line. ? Fill_Table ? Fill_Data ? Build_SQL  On the File menu, click Close and Return to Microsoft Access. Run the UpdateTest query.

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