java - Generate encoding String according to creation order -

I need to create strings for each item included in the database. For example:

  x00001 The first item for the sencond item x00003 for the third item x00002  

The way I decided to do this is the number of rows. Before inserting the third item, I count against the database, I know that there are already 2 rows, so the next encoding is finished with 3. But there is a problem. If I delete the second item, the forward object will not be x00004, but x00003.

I can add additional columns to the table to store the next encoding, I do not know if there are other better solutions?

What do you want SELECT MAX (id) or SELECT Max inside the transaction (some_function (id)) .

As stated in Oded's answer, there are many ways in which the database has its own way of providing sequence and non-numeric ID based on DBMS.

In addition, you can create broken columns in the form of different columns and 00001 and both columns form the primary key; Most of the database sequences will be able to provide.

However, whether or not your primary key should be on this question; Y suggests that the key has some meaning (otherwise you will be content with a plain integer ID).