09 December 2010

Questions regarding quiz on object types (7 December quiz) (1762)

A player wrote the following: Hello Steven, Just a few remarks regarding the last quiz, that I would like to hear your opinion on: 1. Regarding the creation on an object type containing STATIC subprograms only, without any attributes: While it is right that such a type is practically substitutable with a PL/SQL package, as far as I know, in Java this is allowed. Since the object oriented features in Oracle usually attempt "to mimic" the constructs and behavior of other object oriented languages, I don't see any reason for such a construct not being allowed in Oracle as well, at least technically, even if practically it is of course of a limited use. The only limitation might be that such a type should be NOT INSTANTIABLE (and therefore not storable in a database column, a.s.o.). In fact, maybe it might contain MEMBER procedures also and still being without attributes. 2. Regarding the restriction that the methods declarations should always come after the type's attributes: I think that this is also a superfluous restriction. While the order of the attributes is essential, just like the order of the columns in a table, for example for clearly determining the order of the arguments in calling the type's constructor, the order of the methods declarations seems to be not relevant and they can probably come as well in any position inside the type definition, similar to the order of subprograms in a package. This would be more similar to Oracle's general behavior of allowing independent clauses in any CREATE statement to come in any order in most cases. As a quick example, in a table definition you can put constraints before column definitions, like in the following: create table mytab (constraint mytab_pk primary key (x), x number not null); It is true that a reasonable person will probably NOT code things like this, and NONE of the examples in the different documentation sources will ever use such an awkward syntax, but this means that you have practically only 2 ways of knowing that this DOES NOT work: a. either to have tried it out by yourself (which probably nobody did, well ... at least until this quiz ... ) or b. to closely follow-up the complete railroad syntax diagram. I am not sure whether this restriction is explicitely mentioned in the documentation. I would love to read your opinion on these issues. I am quite busy at the moment and do not have time to respond, so I thought I would post this for others to consider. Regards, Steven

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