MS Access query error

Hi all

what is the problem in this code

Code:

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Using cmd As New OleDb.OleDbCommand("update table1 Set column1= (SELECT Count(*) As CountOfID from table2)", con)
            con.Open()
            cmd.ExecuteNonQuery()
            con.Close()
        End Using

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i wrote it to update ms access table but it gives an error "Operation must use an updateable query."

now I'm using Dcount instead but i want to find the problem

thanks in advance