"Campbell, Lance" <lance@xxxxxxxxxxxx> wrote: > I map data from rows in tables to objects in Java. When I map > integers in the database I map them to integer primitives in Java. > The challenge I am running into is what do I do when a table has a > integer foreign key that is null. Ideally when a table in > PostgreSql has a foreign key that does not exist I would like the > value to be zero rather than null. This works really well for me > because I NEVER use a key with the value of 0. I would definitely use NULL in the database to indicate that a value is unknown or not applicable. Really. Always. How you map that to your Java objects is another issue -- if you used an Integer object, you would have a natural mapping of NULL in the database to a Java null and back again. That's what I normally do. In my view, you need a really good reason to map to the primitive, especially since Java has added the automatic boxing and unboxing features. If you feel compelled to micro-optimize to primitives, you need to have some way to map the NULLs to your magic number and back again. The former is pretty easy if you use zero as your magic number, since getInt returns zero for a NULL, leaving it to you to check wasNull to determine whether it's really a NULL or a zero, that direction is easy. http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html#getInt(int) http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html#wasNull() Going the other direction, you need some way to convert a zero in that column to a NULL in the database. Exactly how you do that depends on how you are doing your mapping -- unless you want to try to use PostgreSQL rules to rewrite your statements or some such. -Kevin -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
