Algorithm generating a unique ID based on client name

Question

Following code is supposed generate a new ID (PID) for a new client based on the client name's first letter and the existing IDs in the range which are stored in a database.

For ex lets say if the new client's name is "Abc" and if last ID in the database starting from letter A, is A200. Then the new ID should be A201.

This code compiles and runs giving the desired out put but I hope this could be optimized further.

Expecting your suggestions on improving this...

private void GeneratePIDforNewPoint(string pointName)
{
    string firstLetterOfPointName; // variable to hold first letter of "point name" being passed to this method
    string lastExistingPID; // variable to hold the last PID (most recent hence largest) from the list of PIDs retrieved from the database
    int lastDigitOfExistingPID; // variable to hold last digit of the "lastPID" (ex- digit '2' from PID 'F002')
    string finalPID; // variable to hold out put (the generated new PID for the new point)...


    firstLetterOfPointName = pointName[0]; // Get the fist letter of the point name...

    List<string> pidList=_ds.GetPIDs(firstLetterOfPointName); // Calling method to get the pid list from database

    if (pidList.Count >=1) //  At the end of this if block, numeric part of the new PID will be desided
    {
        pidList.Sort();
        lastExistingPID = pidList[pidList.Count - 1];
        lastDigitOfExistingPID = int.Parse(lastExistingPID[lastExistingPID.Length - 1].ToString());
    }
    else
    {
        lastDigitOfExistingPID = 0;
    }

    lastDigitOfExistingPID += 1;

    // Found digit will be converted to the pid format by attaching the starting letter and zeros to make the length.(format --> A001/ B099 / C100 etc.)


    finalPID= firstLetterOfPointName + String.Format("{0:000}", lastDigitOfExistingPID );
    _view.PID = finalPID;
}


 public List<string> GetPIDs(string firstLetterOfPointName)
        {
            string selectStatement = @"SELECT PID FROM point WHERE PID like @PID";
            List<string> pidList = new List<string>(); // List to store all retrived PIDs from the database...

            // Retrieve all existing PIDs starting with "letter" from the database
            using (SqlConnection sqlConnection = new SqlConnection(db.GetConnectionString))
            {
                using (SqlCommand sqlCommand = new SqlCommand(selectStatement, sqlConnection))
                {
                    sqlCommand.Parameters.Add("@PID", SqlDbType.VarChar).Value = firstLetterOfPointName + '%';
                    sqlConnection.Open();
                    using (SqlDataReader dataReader = sqlCommand.ExecuteReader())
                    {                        
                        // If reader has data, are added to the list
                        while (dataReader.Read())
                        {
                            pidList.Add(dataReader.GetString(0).Trim());
                        }
                        return pidList;
                    }
                }
            }
        }

Answer 1

First, I would expect from a function named GeneratePID to return the generated ID and not to set it. (Nobody likes side-effects)

private string GeneratePIDforNewPoint(string pointName)
{
    if(pointName == null)
        return "error";         

    var storedPIDs = _ds.GetPIDs(pointName[0]);
    var newPID = 0;        
    if(storedPIDs.Count > 0) {
        var maximumStoredPID = _ds.GetPIDs(pointName[0]).Max();
        newPID = Int32.Parse(maximumStoredPID.substring(1)) + 1;
    }
    return pointName[0] + String.Format("{0:000}", newPID); 
}

Answer 2

It's been an old question, just thought to add an alternative to a name-with-counter solution already offered above.

ID using CRC32

ID based on data

Usually when I need an ID that is based on user's full name or some other type of data, I'd do something like this:

php example

class myUtils {
   static public function genID( $firstName, $lastName ) {
      $strDesc = $firstName . "-" . $lastName;
      return "".dechex(crc32($strDesc));
   }
}

This will return an 8-character long string representation of a 32-bit integer, for example: a072c35b

This is then simple and fast to use:

$id = myUtils::genID("First name","Last name");

This way you can generate ID that represents bunch of data grouped together, for example instead of just providing first and last name, you can add his passport number into the mix etc. to generate ID that is unique to that user.

However, if you just require a unique ID number, there's even simpler way:

Just a Unique ID

If I need to generate a unique ID that is just that - unique, I'd go for something like this:

php example

class myUtils {
   static public function uid_32bit() {
      return "".dechex(crc32(date("YdmHis").bin2hex(openssl_random_pseudo_bytes(10))));
   }
   static public function uid_64bit() {
      return self::uid_32bit().self::uid_32bit();
   }
}

This way I could get 8-character long unique string - representing 32-bit integer:

$id = myUtils::uid_32bit();

or, I could get 16-character long unique string, representing 64-bit integer value:

$id = myUtils::uid_64bit();

Main advantage of this approach is that is easily read by humans, as it contains only lowercase letters (a...f) and numbers (0...9), and can be used for instance invoice unique numbers that are shown to user, or some other client-facing output, without revealing any information about how you have structured your data in the back-end.