Faithfully implementing the SQL Standard makes it easy for users to use Derby for applications that have been developed on other DBMS implementations, and also makes it easy for users to develop applications on Derby, then move them to other systems. Both of these are good uses of Derby, and I'm pleased to see them.
Furthermore, implementing the SQL Standard is an effective way to build a high-quality piece of software, for the SQL Standard is the result of decades of work by thousands of very intelligent and hard-working people, who have tried to describe the SQL language as accurately and thoroughly as they can.
That is, in general, the standard specifies reasonable and desirable behavior.
However, there is a major frustration in attempting to implement the SQL standard: it's not freely available. In order to access the official SQL standard, in order to contribute to the development of the official SQL standard, in order to participate in direct discussions with the team of people who maintain and enhance the official SQL standard, you have to have access to the ANSI/ISO world, which is a membership group which costs a substantial amount of money to join. As far as I know, the Apache Software Foundation does not have access to the SQL Standards process, which is a shame.
This leads to problems in:
- access to the official text of the standard
- access to communities for discussions involving interpretation of the standard
- access to tools and test beds for verification of the standard