自动递增ID中断序列

Question

My program has an auto incremented ID with the format of ITM001, ITM002... . But after ITM009, ITM0010 the sequence is broken and goes back to ITM001 . Because of that I'm getting ITM0010 as next item ID instead of ITM0011 . Please help me to understand how should I write the query to continue the sequence.

ITM001
**ITM0010**
ITM002
ITM003
ITM004
ITM005
ITM006
ITM007
ITM008
ITM009

   Connection conn = DBConnection.conn();
      String sql = "select itemId from ItemMain";
       ResultSet res = DBHandller.getData(sql, conn);
        if (res.last()) {
              String lastid = res.getString("itemId");
               return lastid;
        }
        return null;   
/////////////////////////////////////////////////////////////////////////////


              String itemID = ItemController.getItemID();

              String[] split = itemID.split("ITM",0);
              int num = Integer.parseInt(split[1]);
              itemID = "ITM00"+ (num+1);
              txtitemID.setText(itemID);

Answer 1

The problem is that you're using split on 0, and there are several 0's in your String after you increment, for instance:

    String[] split = itemID.split("ITM",0);
    int num = Integer.parseInt(split[1]);
    String second = "ITM00" + (num + 1);
    System.out.println(second);
    System.out.println(Arrays.toString(second.split("0")));

This will output:

[ITM, , 1]

Since the last 0 will also be split.

Something like:

String itemID = "ITM009";
int num = Integer.parseInt(itemID.substring(itemID.indexOf("0")));
String second = "ITM0" + String.format("%02d", num + 1);
System.out.println(second);

Will give you what you want probably, but you need to figure out how many digits you want your key to have and adapt accordingly.

Answer 2

You are implicitly sorting on a VARCHAR field.

SELECT a.a FROM (
    SELECT 'a001' [a]
    UNION ALL
    SELECT 'a009' [a]
    UNION ALL
    SELECT 'a0010' [a]
) a ORDER BY a

a001
a0010
a009

The last id you pick up will always be 009 so the next one you create will always be 0010.

If you front padded the "10" with 1 "0" instead of two the implicit ascending sorting would be correct. "001 ... 009, 010"