使用集合操作符给嵌套表赋值
从
oracle10g
开始，允许将多个嵌套表的结果集合到某个嵌套表中（
set
，
multiset union[distinct]
，
multiset intersect
，
multiset except
）。其中
set
有一个嵌套表传入参数，作用是消除嵌套表中的重复内容；
multiset union
是将两个嵌套表内容合并起来，加入关键词
distinct
可以消除重复内容；
multiset intersect
是将两个嵌套表的共同内容返回并赋值给另外一个嵌套表并自动消除重复；
multiset except
是找出嵌套表
1
中存在但
2
中不存在的元素，需要使用
distinct
关键词消除重复内容。如下为测试代码。
declare
type
number_sets_type
is
table
of
number
;
number_sets1 number_sets_type := number_sets_type(
1
,
2
,
3
,
4
,
3
,
1
);
number_sets2 number_sets_type := number_sets_type(
5
,
6
,
3
,
4
);
number_sets3 number_sets_type;
begin
number_sets3 :=
set
(number_sets1);
for
i
in
number_sets3.
first
..number_sets3.
last
loop
dbms_output.put(number_sets3(i)||
','
);
end
loop
;
dbms_output.new_line;
number_sets3 := number_sets1
multiset
union
number_sets2;
for
i
in
number_sets3.
first
..number_sets3.
last
loop
dbms_output.put(number_sets3(i)||
','
);
end
loop
;
dbms_output.new_line;
number_sets3 := number_sets1
multiset
union
distinct
number_sets2;
for
i
in
number_sets3.
first
..number_sets3.
last
loop
dbms_output.put(number_sets3(i)||
','
);
end
loop
;
dbms_output.new_line;
number_sets3 := number_sets1
multiset
intersect
number_sets2;
for
i
in
number_sets3.
first
..number_sets3.
last
loop
dbms_output.put(number_sets3(i)||
','
);
end
loop
;
dbms_output.new_line;
number_sets3 := number_sets1
multiset
except
number_sets2;
for
i
in
number_sets3.
first
..number_sets3.
last
loop
dbms_output.put(number_sets3(i)||
','
);
end
loop
;
dbms_output.new_line;
number_sets3 := number_sets1
multiset
except
distinct
number_sets2;
for
i
in
number_sets3.
first
..number_sets3.
last
loop
dbms_output.put(number_sets3(i)||
','
);
end
loop
;
dbms_output.new_line;
end
;
1,2,3,4,
1,2,3,4,3,1,5,6,3,4,
1,2,3,4,5,6,
3,4,
1,2,3,1,
1,2,