MS ACCESS - flag duplicates in to the same table

(1) My ACCESS Table1 has following columns, i.e., Field1, Field2, Field3, ..., Field 10 with 750,000 records.

(2) FIELD2 is supposed to contain unique value, but somehow there are over 10,000 duplicate values in it. I found this by using

SELECT Table1.FIELD2, count(Table1.FIELD2) as CheckDupe from Table1 group by 1 where CheckDupe>1

QUESTION:
I'd like to find an effective way to
(A) Make Table1 to have extra column FIELD11 as a flag
(B) FIELD11 = "Yes" If FIELD2 contains duplicate value and "No" when it contains unique value?

I am just an intermediate MS ACCESS level.  I found that the following solution would work, but very inefficient ie.,
(i) Make a text list of dupe values in MS WORD "Value1", "Value2", ...., "Value10000"
(ii) Create an intermediate table (called Table2) from Table1 that contain only 2 fields, i.e., FIELD2 and FIELD11, where as FIELD11 = ""
(iii) write an UPDATE query like this:

UPDATE TABLE2 SET TABLE2.FIELD11 = "Yes"
WHERE TABLE2.FIELD2 IN ("Value1", "Value2", ... , "Value1000");

(iv) run this query. then replace the next thousand values, save and run. then redo this again . . . .  until all 10,000 values are covered.

The problem is 1. I have 5 other tables that have the same problem. I dont want to spend the whole week doing this.  So, Help please.
Paul_ATLAsked:
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Paul_ATLConnect With a Mentor Author Commented:
Hi cyberkiwi,

I works now. I change >0 to >1
Thanks for your help. Save me lots of time.
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cyberkiwiConnect With a Mentor Commented:
Add a new column into Table1 using the UI.
Run this query (if field2 is textual)

update Table1
set Field11 = IIF(DCount("Field2", "Table1", "Field2='" & Field2 & "'")>0,true, false)
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Paul_ATLAuthor Commented:
Hi cyberkiwi,

I did as suggested to add FIELD11.
Then Copy-PASTE your query in to an UPDATE querym but when run, it asks me for "parameter entry" of TABLE1
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Paul_ATLAuthor Commented:
Hi cyberkiwi,

Sorry, I made some typos.

Your query runs, but when checking the result, it only updates FIELD11 with value -1 for all records.
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cyberkiwiCommented:
What type is Field2?

Another approach, make Field11 a Number field, then try this query:

update Table1
set Field11 = DCount("Field2", "Table1", "Field2='" & Field2 & "'")

Actually never mind, I see the error. It should be greater than 1...

update Table1
set Field11 = IIF(DCount("Field2", "Table1", "Field2='" & Field2 & "'")>1,true, false)
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cyberkiwiCommented:
You're welcome! Makes me happy when askers help themselves :)
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Paul_ATLAuthor Commented:
Great advice, just minor issue on >1 instead of >0 but I can figure this out.  But certainly, without his advice, I will NEVER figure to use DCOUNT.

Thanks a bunch
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