利用ROWID快速执行关联更新

一.构造相关表P1,P2

create table p1(id int,name char(10));

create table p2(id int,name char(10));

二.批量插入数据

begin

for i in 1 .. 100000

loop

insert into p1 values(i,'a'||i);

end loop

;

commit;

end;

begin

for i in 1 .. 100000

loop

insert into p2 values(i,'b'||i);

end loop

;

commit;

end;

三 对比测试

本来的需求:

update p1 set name=(select name from p2 where p1.id=p2.id);

用p2表的name列来更新p1表的name列

SQL> set timing on

SQL> update p1 set name=(select name from p2 where p1.id=p2.id);

100000 rows updated.

Elapsed: 00:09:59.68

直接update花了10分钟,太慢了

利用rowid更新

DECLARE

  CURSOR cur IS

    SELECT

     b.name, a.ROWID ROW_ID

      FROM p1 a, p2 b

     WHERE a.id = b.id

     ORDER BY a.ROWID;

  V_COUNTER NUMBER;

BEGIN

  V_COUNTER := 0;

  FOR row IN cur LOOP

    UPDATE p1

       SET name = row.name

     WHERE ROWID = row.ROW_ID;

    V_COUNTER := V_COUNTER + 1;

    IF (V_COUNTER >= 1000) THEN

      COMMIT;

      V_COUNTER := 0;

    END IF;

  END LOOP;

  COMMIT;

END;

PL/SQL procedure successfully completed.

Elapsed: 00:00:19.56

差距太明显了--------------------------------------------------