CREATE TYPE Dept_t1
/
CREATE TYPE Emp_t1 AS OBJECT(
eno number(4),
ename varchar2(15),
edept ref dept_t1,
salary number(8,2));
/
CREATE TYPE Dept_t1 AS OBJECT(
dno number(2),
dname varchar2(12),
mgr ref emp_t1);
/
CREATE TYPE Proj_t1 AS OBJECT(
pno number(4),
pname varchar2(15),
pdept ref dept_t1,
budget number(10,2));
/
CREATE TABLE Emp1 OF Emp_t1(
eno PRIMARY KEY
);
CREATE TABLE Dept1 OF Dept_t1(
dno PRIMARY KEY
);
CREATE TABLE Proj1 OF Proj_t1(
pno PRIMARY KEY
);
ALTER TABLE Emp1 MODIFY (edept REFERENCES Dept1);
ALTER TABLE Dept1 MODIFY (mgr REFERENCES Emp1);
ALTER TABLE Proj1 MODIFY (pdept REFERENCES dept1);
INSERT INTO Emp1 VALUES(1,'A',(SELECT REF(d) FROM Dept1 d where d.dno=11),30)
/
INSERT INTO Emp1 VALUES(2,'B',(SELECT REF(d) FROM Dept1 d where d.dno=12),50)
/
INSERT INTO Dept1 VALUES(11,'D1',(SELECT REF(e) FROM Emp1 e where e.eno=1))
/
INSERT INTO Dept1 VALUES(12,'D2',(SELECT REF(e) FROM Emp1 e where e.eno=2))
/
INSERT INTO Proj1 VALUES(111,'P1',(SELECT REF(e) FROM Dept1 e where e.dno=11),25)
/
INSERT INTO Proj1 VALUES(112,'P2',(SELECT REF(e) FROM Dept1 e where e.dno=12),35)
/
当我尝试执行以下查询时，SELECT p.pname,p.pdept.dno FROM Proj1 p WHERE p.budget>45
p.pdept.dno 列变空。如何解决这个问题？我已经添加了所有值。但不确定为什么会显示空值。我是对象关系数据库管理系统的新手。所以我需要你们所有人的帮助。
Dept1 表格图像是这样的。
