How to limt new records added to an Access 2013 table?

How can I create an Access form which will only allow the user to enter just one record into a table.  This form will be emailed to a client, and will need this feature in order to avoid duplication.  Thanks
Eric BurtonSr.ProgrammerAsked:
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Scott McDaniel (Microsoft Access MVP - EE MVE )Infotrakker SoftwareCommented:
Do you mean the TABLE will hold only one record, or do you mean the Table will hold multiple records, but you want your client to one enter one?

If the first, then just check the record count of the table before you allow the form to update:

Sub Form_BeforeUpdate(Cancel as Integer)
  If Me.NewRecord Then
    If DCount("SomeField", "YourTableName") >0 Then
      MsgBox "You cannot add more records"
      Cancel = True
    End If
  End If
End Sub

If the second, then the best way to prevent duplication is to add a Unique Index to the table, and include the Fields that would define a duplicate record. For example, in a Customer table, I might consider the CustomerName, CustomerZip and CustomerPhone to be unique. If so, then I'd create an Index on the table, and include all three of those fields, and set the Unique property to True.
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Gustav BrockCIOCommented:
Have a field of data type Long Integer with a default value of 0 (zero) and set this as the Primary Key.
Don't show the field on the form.
The client may create, update, or delete this single record but cannot add another record.

/gustav
0

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