bulk collect可以将查询结果一次性地加载到collections中，而不用一条一条地处理。
在select into,fetch into,returning into语句使用使用bulk collect时，所有的into变量都必须是collections。
create table jy ( object_id number(12), object_name varchar2(20), object_type varchar2(20) )
在select into语句中使用bulk collect
declare
type object_list is table of jy.object_name%type;
objs object_list;
begin
select object_name bulk collect
into objs
from jy;
for r in objs.first .. objs.last loop
dbms_output.put_line(''|| objs(r));
end loop;
end;
/
在fetch into中使用bulk collect
declare
type objecttab is table of jy%rowtype;
objs objecttab;
cursor cob is
select object_id, object_name, object_type
from jy;
begin
open cob;
fetch cob bulk collect
into objs;
close cob; -- 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
for r in objs.first .. objs.last loop
dbms_output.put_line(' ' || objs(r).object_name);
end loop;
end;
declare
type objecttab is table of jy%rowtype;
objs objecttab;
cursor cob is
select object_id, object_name, object_type
from jy;
begin
open cob;
loop
fetch cob bulk collect
into objs limit 100;--每次取一百条数据这是可以根据你的数据库性能来决定的
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;
在returning into中使用bulk collect
declare
type id_list is table of jy.object_id%type;
ids id_list;
type name_list is table of jy.object_name%type;
names name_list;
begin
delete from jy 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;
ORACLE批量绑定FORALL与BULK COLLECT
FORALL与BULK COLLECT的使用方法:
1．使用FORALL比FOR效率高，因为前者只切换一次上下文，而后者将是在循环次数一样多个上下文间切换。
2．使用BLUK COLLECT一次取出一个数据集合，比用游标条取数据效率高，尤其是在网络不大好的情况下。但BLUK COLLECT需要大量内存。
create table test_forall ( user_id number(10), user_name varchar2(20));
select into 中使用bulk collect
DECLARE
TYPE table_forall IS TABLE OF test_forall%ROWTYPE;
v_table table_forall;
BEGIN
SELECT mub.user_id,mub.user_name
BULK COLLECT INTO v_table
FROM mag_user_basic mub
WHERE mub.user_id BETWEEN 10000 AND 10100;
FORALL idx IN 1..v_table.COUNT
INSERT INTO test_forall VALUES v_table(idx);
--VALUES(v_table(idx).user_id,v_table(idx).user_name);Error
--在PL/SQL中，BULK In-BIND与RECORD，%ROWTYPE是不能在一块使用的，
--也就是说，BULK In-BIND只能与简单类型的数组一块使用
COMMIT;
EXCEPTION
WHEN OTHERS THEN
ROLLBACK;
END;
fetch into 中使用bulk collect
DECLARE
TYPE table_forall IS TABLE OF test_forall%ROWTYPE;
v_table table_forall;
CURSOR c1 IS
SELECT mub.user_id,mub.user_name
FROM mag_user_basic mub
WHERE mub.user_id BETWEEN 10000 AND 10100;
BEGIN
OPEN c1;
--在fetch into中使用bulk collect
FETCH c1 BULK COLLECT INTO v_table;
FORALL idx IN 1..v_table.COUNT
INSERT INTO test_forall VALUES v_table(idx);
COMMIT;
EXCEPTION
WHEN OTHERS THEN
ROLLBACK;
END;
在returning into中使用bulk collect
CREATE TABLE test_forall2 AS SELECT * FROM test_forall;
—-在returning into中使用bulk collect
DECLARE
TYPE IdList IS TABLE OF test_forall.User_Id%TYPE;
enums IdList;
TYPE NameList IS TABLE OF test_forall.user_name%TYPE;
names NameList;
BEGIN
DELETE FROM test_forall2 WHERE user_id = 10100
RETURNING user_id, user_name BULK COLLECT INTO enums, names;
dbms_output.put_line('Deleted ' || SQL%ROWCOUNT || ' rows:');
FOR i IN enums.FIRST .. enums.LAST
LOOP
dbms_output.put_line('User #' || enums(i) || ': ' || names(i));
END LOOP;
COMMIT;
EXCEPTION
WHEN OTHERS THEN
ROLLBACK;
END;
–批量更新中，将for改成forall
DECLARE
TYPE NumList IS VARRAY(20) OF NUMBER;
depts NumList := NumList(10, 30, 70, ...);
-- department numbers
BEGIN
/*FOR i IN depts.FIRST..depts.LAST
LOOP
...
--UPDATE statement is sent to the SQL engine
-- with each iteration of the FOR loop!
UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);
END LOOP:
*/
FORALL i IN depts.FIRST..depts.LAST
UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);
commit;
END;