输入参考范围

Question

我正在研究数据库,目前正在研究对象关系数据库项目,我遇到了一个关于对象表中可能的约束数量的小问题.我正在使用Hector Garcia-Molina(和其他作者)的"数据库系统:完整的书"作为参考,并且有一个像这样的通用SQL示例:

CREATE TYPE StarType AS (
  name CHAR(30),
  address AddressType,
  bestMovie REF(MovieType) SCOPE Movies
);

现在,我的项目中有一种类似的类型,因为它也使用类型中的另一种类型的引用,但是在那里放置引用的子句不包括Oracle中的SCOPE(至少我还没有找到它)在文档中它输出错误).所以我有这样的类型:

CREATE OR REPLACE TYPE "ApplicationType" AS OBJECT (
  "person" REF "PersonType",
  "competition" REF "CompetitionType",
  "dateApplied" DATE
);
/

......有效.但是当我想约束REF列时,我只能约束一个,如下所示:

CREATE TABLE "Applications" OF "ApplicationType" (
  "person" SCOPE IS "People" /* or "competition" SCOPE IS "Competitions" */
)
OBJECT IDENTIFIER IS SYSTEM GENERATED;

有没有办法为两个REF列提供约束？

Answer 1

这很好用:

CREATE TABLE Applications OF ApplicationType (
  person SCOPE IS People,
  competition SCOPE IS Competitions
)
OBJECT IDENTIFIER IS SYSTEM GENERATED;

也许您尝试使用or而不是,分隔约束来创建表(如您的注释中所示).

测试约束也很容易.只需创建这两个额外的虚拟表:

CREATE TABLE People2 OF PersonType
OBJECT IDENTIFIER IS SYSTEM GENERATED;

CREATE TABLE Competitions2 OF CompetitionType
OBJECT IDENTIFIER IS SYSTEM GENERATED;

然后:

INSERT INTO People VALUES('p1');
INSERT INTO People2 VALUES('p21');
INSERT INTO Competitions VALUES('c1');
INSERT INTO Competitions2 VALUES('c21');
COMMIT;
INSERT INTO Applications
VALUES
(
   (SELECT REF(p) FROM People p WHERE person = 'p1'),
   (SELECT REF(c) FROM Competitions2 c WHERE competition = 'c21'),
   SYSDATE
);

导致ORA-22889,因为引用的值不在指定的范围表中(竞争对手,而不是虚拟竞赛2).您可以使用People2而不是People进行类似的测试.