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--------------------------------------------------