Check constraint on a type

问题

I have something like this:

CREATE TYPE oAuthors AS OBJECT (
    ... ,
    contract CHAR(1),

    CONSTRUCTOR FUNCTION oAuthors (...
);

The thing is that I wanted to add a constraint to allow only 0 or 1 in contract.
I tried to do so right after the declaration of the column by adding

CONSTRAINT contract_bit CHECK (contract IN ('0','1')),

I also tried to do it in an ALTER sentence, but the problem is that this is not a table so it won't recognize it, and using ALTER TYPE doesn't work (although I was just trying, I don't know how to do it).

So basically I have no idea if this is possible by using a constraint, should I create a trigger or something?

回答1:

You can't define constraint on object type: http://docs.oracle.com/cd/B28359_01/server.111/b28286/clauses002.htm

You can define constraints syntactically in two ways:

• As part of the definition of an individual column or attribute. This is called inline specification.
• As part of the table definition. This is called out-of-line specification

Constraint clauses can appear in the following statements:

• CREATE TABLE (see CREATE TABLE)
• ALTER TABLE (see ALTER TABLE)
• CREATE VIEW (see CREATE VIEW)
• ALTER VIEW (see ALTER VIEW)

Here is how you enforce constraints on objects: http://docs.oracle.com/cd/B28359_01/appdev.111/b28371/adobjdes.htm#i452285

来源：https://stackoverflow.com/questions/23954390/check-constraint-on-a-type