案例讨论：批量删除Oracle数据库的数据
在使用delete语句删除数据时，数据库是要做日志记录的，以便将来可以恢复数据，可是我在删除上百万条数据时，十分缓慢甚至死机，请问有没有什么好方法?
网友观点一:
create or replace procedure delete_table
is
i number(10);
begin
for x in (select * from emp where DEPTNO like 'a%')
loop
delete emp where emp.id = x.id
i:=i+1;
if i>1000 then
commit;
i:=0;
end if;
end loop;
exception
when others then
dbms_out.put_line(sqlcode);
rollback;
end delete_table;
网友观点二:
这个是我平常用来批量删除数据，每500条数据提交一次。
DECLARE
CNT NUMBER(10):=0;
I NUMBER(10);
BEGIN
SELECT COUNT(*) INTO CNT FROM ep_arrearage_bak WHERE TO_CHAR(DF_DATE,'MM')='01';
FOR I IN 1..TRUNC(CNT/500)+1 LOOP
DELETE FROM ep_arrearage_bak WHERE TO_CHAR(DF_DATE,'MM')='01' AND ROWNUM<=500;
COMMIT;
END LOOP;
END;
专家意见:几个办法:
1. 如果删除的数据是大部分,建议使用楼上的方法把要保留的数据放在一个临时表里,truncate table后再放回来
2. 也可以分段提交,楼上也提到了
3. 专门使用一个大回滚段
4. 如果确认将来不需要做恢复,改为非归档模式,删除完改回来再做个备份.
专家给出的解决方案:
有条件的分步删除数据表中的记录
--创建测试表
create table test as select * from dba_objects;
Table created.
--创建删除表的存储过程
create or replace procedure deleteTab
--插入语句
SQL> insert into test select * from dba_objects;
6374 rows created.
SQL> /
6374 rows created.
SQL> /
6374 rows created.
SQL> commit;
--创建删除的存储过程
create or replace procedure deleteTab
/**
** Usage: run the script to create the proc deleteTab
** in SQL*PLUS, type "exec deleteTab('Foo','ID>=1000000','3000');"
** to delete the records in the table "Foo", commit per 3000 records.
** Condition with default value '1=1' and default Commit batch is 10000.
**/
(
p_TableName in varchar2, -- The TableName which you want to delete from
p_Condition in varchar2 default '1=1', -- Delete condition, such as "id>=100000"
p_Count in varchar2 default '10000' -- Commit after delete How many records
)
as
pragma autonomous_transaction;
n_delete number:=0;
begin
while 1=1 loop
EXECUTE IMMEDIATE
'delete from '||p_TableName||' where '||p_Condition||' and rownum <= :rn'
USING p_Count;
if SQL%NOTFOUND then
exit;
else
n_delete:=n_delete + SQL%ROWCOUNT;
end if;
commit;
end loop;
commit;
DBMS_OUTPUT.PUT_LINE('Finished!');
DBMS_OUTPUT.PUT_LINE('Totally '||to_char(n_delete)||' records deleted!');
end;
/
--执行语句
SQL> exec deleteTab('TEST','object_id >0','10000')
你看看执行结果我试验过，效果还可以