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How to solve the "Cannot Update Identity Column" error

Posted on 2009-03-29
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Last Modified: 2012-05-06
I am trying to find a solution to that byt nothing ....
I change a field in my Personnel table To Identity Specification ..
While I am trying to update my table adapter i got this error as an exception in my try Catch ...
Plz someone guide me ...
this seems to me that the sql server cannot generate the next [A/A] (A/A is the field i changed)
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Expert Comment

by:carlnorrbom
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Hi,

If you have the column set to identity specification you should also set AutoIncrement to true (if you don't have any perticular logic to handle the automatic incrementation already) and seed to whatever suits your application (usually 1). Also, if you in existing logic have insert / update queries putting / updating values of that particular column you need to rewrite them to exclude the identity specification column.

/Carl.
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by:John (Yiannis) Toutountzoglou
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yes i did that in sql server
I modify the table and i did set seed and increament to 1
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by:carlnorrbom
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Hi,

Yes, but have you updated the sql queries for update / insert to reflect this change?

/Carl.
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Author Comment

by:John (Yiannis) Toutountzoglou
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you mean to configure the dataset again?
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by:carlnorrbom
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Hi,

Otherwise, try using SET IDENTITY_INSERT <tablename> ON , i.e. (SQL Code example for copying between two tables):

ALTER TABLE <tablename> DISABLE TRIGGER MyTrigger

SET IDENTITY_INSERT <tablename> ON

INSERT INTO <tablename> (IDCol, Col1, Col2, Col3, Col4)
  SELECT IDCol, Col1, Col2, Col3, Col4 FROM <tablename2>
  WHERE IDCol=<value>

SET IDENTITY_INSERT <tablename> OFF

ALTER TABLE <tablename> ENABLE TRIGGER MyTrigger

/Carl.
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Author Comment

by:John (Yiannis) Toutountzoglou
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before that ....let me ask you something
my [A/A] filed is not my primary KEy
primary key is Key_Personnel which is identity specificationi
i saw that i am not allowed to set 2 fileds with identity.

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Expert Comment

by:carlnorrbom
Comment Utility
Hi,

Ok, there is really no point in having two fields as identity. The reason for an identity field is to ensure unique identification of each commited row. My recommendation would be to have one field acting as both primary key / identity specification with autoincrement.

/Carl.
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Author Comment

by:John (Yiannis) Toutountzoglou
Comment Utility
so can i use for the [A/A] field this?
Dim lastrow As Int32
       lastrow = PersonnelDataSet.Tables(0).Rows.Count - 1
       A_ATextBox.Text = CStr(CDbl(CDbl(PersonnelDataSet.Tables(0).Rows(lastrow).Item(1).ToString) + 1))
in my form load event? this one just add +1 increament in the last A/A
is this logical? would this work?

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Author Comment

by:John (Yiannis) Toutountzoglou
Comment Utility
my dought is about duplicates values
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carlnorrbom earned 500 total points
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Hi,

You can do a select which will get the highest value from the colum in question before you perform an insert in order to make sure you avoid duplicates, i.e.

strMax = "SELECT MAX(A/A) AS MaxCount FROM YourTableName"
Dim maxCount As New SqlCommand(strMax, YourSqlConnection)
Dim maxAA As Integer = maxCount.ExecuteScalar()
Dim newAA As Integer = maxAA + 1

then in Your insert query -> insert the value for newAA..

/Carl.
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by:John (Yiannis) Toutountzoglou
Comment Utility
Sorry for my delay.....i was Flying To brussels and back to greece.
It works ....
here is what i've done according to your suggestion...
i increase the point value...but check my code for other suggestion..thank you very much....


 Me.PersonnelBindingSource.AddNew()

       

        Dim conn As New SqlConnection(My.Settings.MyconnectionString)

        If conn.State = ConnectionState.Open Then conn.Close()

        conn.Open()
 

        Dim strMax As String = "SELECT MAX([A/A]) AS MaxCount FROM Personnel"

        Dim maxCount As New SqlCommand(strMax, conn)

        Dim maxAA As Integer = CInt(maxCount.ExecuteScalar())

        Dim newAA As Integer = maxAA + 1

        

A_ATextBox.Text = CStr(newAA)

        ..

..

..
 

        conn.close()

Open in new window

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Author Closing Comment

by:John (Yiannis) Toutountzoglou
Comment Utility
Plz check my last comment and correct me if for any mistakes ...
note that ...all my code is in my form load event...
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Expert Comment

by:carlnorrbom
Comment Utility
Hi,

It seems to check out.

/Carl.
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