Oracle 的 bulk collect用法——批量查询

采用bulk collect可以将查询结果一次性地加载到collections中，而不是通过cursor一条一条地处理。

可以在select into,fetch into,returning into语句使用bulk collect。

注意：在使用bulk collect时，所有的into变量都必须是collections。

create table t_test as

select object_id, object_name, object_type

from dba_objects

where wner = 'TEST';

1、在select into语句中使用bulk collect

declare

type object_list is table of t_test.object_name%type;

objs object_list;

begin

select object_name bulk collect

into objs

from t_test

where rownum <= 100;

for r in objs.first .. objs.last loop

dbms_output.put_line(' objs(r)=' || objs(r));

end loop;

end;

/

2、在fetch into中使用bulk collect

declare

type objecttab is table of t_test%rowtype;

objs objecttab;

cursor cob is

select object_id, object_name, object_type

from t_test

where rownum <= 10;

begin

open cob;

fetch cob bulk collect

into objs;

close cob;

for r in objs.first .. objs.last loop

dbms_output.put_line(' objs(r)=' || objs(r).object_name);

end loop;

end;

/

以上为把结果集一次fetch到collect中，我们还可以通过limit参数，来分批fetch数据，如下：

declare

type objecttab is table of t_test%rowtype;

objs objecttab;

cursor cob is

select object_id, object_name, object_type

from t_test

where rownum <= 10000;

begin

open cob;

loop

fetch cob bulk collect

into objs limit 1000;

exit when cob%notfound;

dbms_output.put_line('count:' || objs.count || ' first:' || objs.first ||

' last:' || objs.last);

for r in objs.first .. objs.last loop

dbms_output.put_line(' objs(r)=' || objs(r).object_name);

end loop;

end loop;

close cob;

end;

/

你可以根据实际来调整limit参数的大小，来达到最优的性能。limit参数会影响到PGA的使用率。

3、在returning into中使用bulk collect

declare

type id_list is table of t_test.object_id%type;

ids id_list;

type name_list is table of t_test.object_name%type;

names name_list;

begin

delete from t_test

where object_id <= 87510 returning object_id, object_name bulk collect into ids,

names;

dbms_output.put_line('deleted ' || sql%rowcount || ' rows:');

for i in ids.first .. ids.last loop

dbms_output.put_line('object #' || ids(i) || ': ' || names(i));

end loop;

end;

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原文链接：http://www.linuxidc.com/Linux/2011-09/42096p2.htm