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Oracle 10g PLSQL New Features (Part 3) - Enhancements To PLSQL Collections (ctd)

Oracle 10g PLSQL new features part 1 covered PLSQL regular expressions and compiler enhancements and part 2 started our look at enhancements to PL/SQL collections which continues here.

PLSQL Collection Enhancements

Having looked at comparing nested table collections (part 2), let's


look at using the set operators CARDINALITY, IS [NOT] A SET, IS [NOT] EMPTY to determine the properties of a nested table collection.

Then in Oracle 10g PLSQL new features part 4 we'll look at how to assign to nested tables using the set operators MULTISET UNION [DISTINCT] , 
MULTISET INTERSECT [DISTINCT], MULTISET EXCEPT [DISTINCT] and SET.

Using Set Operators On Oracle 10g PLSQL Collections

Example 1 - CARDINALITY

The cardinality function returns the count of the number of elements in a nested table type collection. The points to note with this function are that an empty set returns a count of 0 as expected but a null set returns a value of NULL.

declare
type BOOK_LIST is table of varchar2(100);
oracle_books book_list :=
book_list('Oracle 10g New Features'
,'Oracle 10g PLSQL New Features'
,'Oracle 10g Application Server');

empty_list book_list := book_list();
other_books book_list;

begin
  dbms_output.put_line('cardinality of oracle_books is '|| cardinality(oracle_books));
  dbms_output.put_line('no. of books in other_books is '|| cardinality(other_books));
  dbms_output.put_line('no. of books in empty_list is '|| cardinality(empty_book_list));
end;

Example 1 produces the following results:

cardinality of oracle_books is 3
number of books in other_books is
number of books in empty_book_list is 0

Example 2 - IS [NOT] EMPTY

This PLSQL operator returns TRUE if a collection is empty or FALSE otherwise and of course the results can be inverted by use of the optional NOT operator.

declare
type book_list is table of varchar2(100);
oracle_books book_list;
oracle_books_2 book_list := book_list();
oracle_books_3 book_list := book_list(
'PLSQL New Features',
'Oracle 10g New Features','Oracle 10g Application Server');

begin
    if oracle_books is empty then 
          dbms_output.put_line('oracle_books is empty');
    elsif oracle_books is null then 
          dbms_output.put_line('oracle_books is null');
    end if;
    if oracle_books_2 is empty then 
          dbms_output.put_line('oracle_books_2 is empty');
    else dbms_output.put_line('oracle_books_2 NOT empty');
    end if;
    if oracle_books_3 is not empty then
         dbms_output.put_line ('oracle_books_3 NOT empty'); end if;
end;

Example 2 produces the following results:

oracle_books is null
oracle_books_2 is empty
oracle_books_3 NOT empty

Example 3 - IS [NOT] A SET 

This is used to test whether or not a given PLSQL collection has all unqie elements. If any duplicates are found or the collection is null then it is not a set. 

declare
type book_list is table of varchar2(100);
null_list book_list;
empty_list book_list := book_list();

oracle_books book_list := book_list('PLSQL New Features',
'Oracle 10g New Features','Oracle 10g Application Server');

plsql_books book_list := book_list('PLSQL New Features',
'PLSQL New Features','PLSQL New Features');

rslt VARCHAR2(4);

begin

if empty_list is not a set then rslt := 'NOT '; end if;
dbms_output.put_line('empty_list is '||rslt||'a set');

if null_list is a set then rslt := null; 
else 
rslt := 'NOT '; end if;
dbms_output.put_line('null_list is '||rslt||'a set');

if plsql_books is not a set then rslt := 'NOT '; 
else rslt := null; end if;
dbms_output.put_line('plsql_books is '||rslt||'a set'); 

if oracle_books is not a set then rslt := 'NOT '; 
else rslt := null; end if;
dbms_output.put_line('oracle_books is '||rslt||'a set'); 

end;

Example 3 produces the following results:

empty_list is a set
null_list is NOT a set
plsql_books is NOT a set
oracle_books is a set

The remaining collection enhancements in Oracle 10g PLSQL are covered in part 4.


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