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

CHAPTER 10 ■ DATABASE TABLES 399
EMPNO ENAME
---------- ----------
7782 Clark
7876 Adams
7521 Ward
7654 Martin
7698 Blake
7900 James
6 rows selected.
Again, this is not a thoroughly documented and supported feature. It has a specific functionality
for EXP and IMP to work. This is the only environment it is assured to work in. Use it at
your own risk, and resist putting it into production code. In fact, if you find you need to use it,
then by definition you didn’t mean to use a nested table at all! It is the wrong construct for
you. Use it for one-off fixes of data or to see what is in the nested table out of curiosity. The
supported way to report on the data is to un-nest it like this:
ops$tkyte@ORA10G> select d.deptno, d.dname, emp.*
2 from dept_and_emp D, table(d.emps) emp
3 /
This is what you should use in queries and production code.
Nested Table Storage
We have already seen some of the storage of the nested table structure. In this section, we’ll
take an in-depth look at the structure created by Oracle by default and what sort of control
over that we have. Working with the same CREATE statement as before
ops$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 emps_empno_unique
2 unique(empno)
3 /
Table altered.
we know that Oracle really creates a structure like the one shown in Figure 10-11.