Finding duplicate records in field using ArcGIS for Desktop?

Question

I'm looking for duplicate records in dbf files based upon the attribute called 'ID'. I have various dbf files from 500,000 records to 1.5 million and I know there are a host of duplicates.

I would like to add a field 'Duplicate' that says Yes or No (or 1 or 0 is fine) when the ID attribute is present elsewhere. Using the following python script in Field Calculator returns 1 for a duplicate entry and 0 for unique entry;

uniqueList = []
def isDuplicate(inValue):
  if inValue in uniqueList:
    return 1
  else:
    uniqueList.append(inValue)
    return 0
isDuplicate(!FIELD_NAME!)

However, the 1st record of, for example, 5 duplicate IDs will also be returned as a 0 (the subsequent 4 are considered the duplicates). I would need all 5 to be marked as duplicate as the ID exists elsewhere.

Using the following code will give you an incremental count of how many times that ID occurs with 1 meaning the 1st occasion and so forth;

UniqueDict = {}
def isDuplicateIndex(inValue):
    UniqueDict.setdefault(inValue,0)
    UniqueDict[inValue] += 1
    return UniqueDict[inValue]

isDuplicateIndex( !YOUR_FIELD! )

I just want a 1 (or Yes) if the ID of that record exists elsewhere! (ArcGIS version 10.1)

I have seen other answers such as Python script for identifying duplicate records (follow up) but it doesn't quite work.

Answer 1

An alternative solution is to use the existing "summary statistics" tool in ArcGIS, then you join the resulting table based on you ID field. The duplicates will have a "COUNT" larger than 1, so it is then simple to calculate it with your field calculator.

Answer 2

The following script creates a new field with the number of occurrences of each value from a specified field. So, for ex, if you have "Paris" 6 times in that field, each row with "Paris" will get a 6.

import arcpy

arcpy.env.workspace=r"D:\test.gdb"
infeature="sample_feature"
field_in="sample_field"
field_out="COUNT_"+field_in

#create the field for the count values
arcpy.AddField_management(infeature,field_out,"SHORT")

#creating the list with all the values in the field, including duplicates
lista=[]
cursor1=arcpy.SearchCursor(infeature)
for row in cursor1:
    i=row.getValue(field_in)    
    lista.append(i)
del cursor1, row

#updating the count field with the number on occurrences of field_in values
#in the previously created list
cursor2=arcpy.UpdateCursor(infeature)
for row in cursor2:
    i=row.getValue(field_in)
    occ=lista.count(i)   
    row.setValue(field_out,occ)
    cursor2.updateRow(row)
del cursor2, row
print ("Done.")

It can be easily modified so that you can have "Yes" or 1 if count>1, but I guess that having the actual count number is more useful.

Later Edit: Or you could use this in field calculator. Pre-Logic script Code:

infeature="sample_feature" #change with the name of your feature
lista=[]
field="sample_field" #change with your field with duplicates
cursor1=arcpy.SearchCursor(infeature)
for row in cursor1:
    i=row.getValue(field)    
    lista.append(i)
del cursor1, row

def duplicates(field_in):        
    occ=lista.count(field_in)
    return occ

duplicate field=

duplicates(!sample_field!)

Answer 3

Another alternative solution (only works with SDE environments) is to use the existing SQL functionality in ArcGIS to show the duplicate records

Get Duplicate Records in Table (Select by Attribute)

[FIELD_NAME] In (SELECT [FIELD_NAME] FROM [TABLE_NAME] GROUP BY [FIELD_NAME] HAVING Count(*)>1 )

Example:

ID In (SELECT ID FROM GISDATA.MY_TABLE GROUP BY ID HAVING Count(*)>1 )