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== MULTISET Operator==

MULTISET operator gets a nested table whose elements are set to certain elements of two nested tables that are input to MULTISET. There are three MULTISET operators:
MULTISET UNION Returns a nested table whose elements are set to the elements of the two input nested tables.
MULTISET INTERSECT Returns a nested table whose elements are set to the elements that are common to the two input nested tables.
MULTISET EXCEPT Returns a nested table whose elements are in the first input nested table but not in the second.
You may also use one of the following options with MULTISET:
ALL Indicates that all applicable elements in the input nested tables are set in the returned nested table. ALL is the default.
DISTINCT Indicates that only the distinct non-duplicate elements in the input nested tables are set in the returned nested table.



<source lang="sql">
SQL>
SQL> CREATE OR REPLACE PROCEDURE multiset_example AS
2 TYPE nestedTableType IS TABLE OF VARCHAR2(10);
3 myTable1 nestedTableType;
4 myTable2 nestedTableType;
5 myTable3 nestedTableType;
6 count_var INTEGER;
7 BEGIN
8 myTable1 := nestedTableType("F", "G", "S");
9 myTable2 := nestedTableType("G", "S", "R");
10
11 myTable3 := myTable1 MULTISET UNION myTable2;
12 DBMS_OUTPUT.PUT("UNION: ");
13 FOR count_var IN 1..myTable3.COUNT LOOP
14 DBMS_OUTPUT.PUT(myTable3(count_var) || " ");
15 END LOOP;
16 DBMS_OUTPUT.PUT_LINE(" ");
17
18 myTable3 := myTable1 MULTISET UNION DISTINCT myTable2;
19 DBMS_OUTPUT.PUT("UNION DISTINCT: ");
20 FOR count_var IN 1..myTable3.COUNT LOOP
21 DBMS_OUTPUT.PUT(myTable3(count_var) || " ");
22 END LOOP;
23 DBMS_OUTPUT.PUT_LINE(" ");
24
25 myTable3 := myTable1 MULTISET INTERSECT myTable2;
26 DBMS_OUTPUT.PUT("INTERSECT: ");
27 FOR count_var IN 1..myTable3.COUNT LOOP
28 DBMS_OUTPUT.PUT(myTable3(count_var) || " ");
29 END LOOP;
30 DBMS_OUTPUT.PUT_LINE(" ");
31
32 myTable3 := myTable1 MULTISET EXCEPT myTable2;
33 DBMS_OUTPUT.PUT_LINE("EXCEPT: ");
34 FOR count_var IN 1..myTable3.COUNT LOOP
35 DBMS_OUTPUT.PUT(myTable3(count_var) || " ");
36 END LOOP;
37 END multiset_example;
38 /
Procedure created.
SQL> CALL multiset_example();
UNION: F G S G S R
UNION DISTINCT: F G S R
INTERSECT: G S
EXCEPT:
Call completed.
SQL></source>

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в 13:45, 26 мая 2010

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