Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

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CHAPTER 10 ■ DATABASE TABLES
7 hiredate date,
8 sal number(7, 2),
9 comm number(7, 2)
10 );
11 /
Type created.
ops$tkyte@ORA10GR1> create or replace type emp_tab_type
2 as table of emp_type
3 /
Type created.
To create a table with a nested table, we need a nested table type. The preceding code creates
a complex object type, EMP_TYPE, and a nested table type of that, EMP_TAB_TYPE. In PL/SQL,
this will be treated much like an array would. In SQL, it will cause a physical nested table to be
created. Here is the simple CREATE TABLE statement that uses it:
ops$tkyte@ORA10G> create table dept_and_emp
2 (deptno number(2) primary key,
3 dname varchar2(14),
4 loc varchar2(13),
5 emps emp_tab_type
6 )
7 nested table emps store as emps_nt;
Table created.
ops$tkyte@ORA10G> alter table emps_nt add constraint
2 emps_empno_unique unique(empno)
3 /
Table altered.
The important part of this CREATE TABLE is the inclusion of the column EMPS of EMP_TAB_
TYPE and the corresponding NESTED TABLE EMPS STORE AS EMPS_NT. This created a real physical
table, EMPS_NT, separate from and in addition to the table DEPT_AND_EMP. We add a constraint
on the EMPNO column directly on the nested table to make the EMPNO unique as it was in our
original relational model. We cannot implement our full data model; however, there is the
self-referencing constraint:
ops$tkyte@ORA10G> alter table emps_nt add constraint mgr_fk
2 foreign key(mgr) references emps_nt(empno);
alter table emps_nt add constraint mgr_fk
*
ERROR at line 1:
ORA-30730: referential constraint not allowed on nested table column
This will simply not work. Nested tables do not support referential integrity constraints,
as they cannot reference any other table—even themselves. So, we’ll just skip that for now.
Next, we’ll populate this table with the existing EMP and DEPT data: