銆愬簲鐢ㄥ満鏅?br /> 琛╰est姣忚淇濆瓨涓涓彿鐮佹(hm0, hm1)錛屼笉鍚岃褰曠殑鍙風爜孌典笉浼氬嚭鐜頒氦鍙夈傞渶楂樻晥鍦板垽鏂嚭鏌愪釜鍙風爜鏄惁鍑虹幇鍦ㄦ煇涓彿鐮佹涓?/p>
-- 寤烘祴璇曡〃
create table test (
hm0 number(8) not null, -- 鍙風爜璧?br />
hm1 number(8) not null -- 鍙風爜姝?br />
);
-- 鎻掑叆2涓囨潯鏁版嵁
begin
for i in 1..20000 loop
insert into test values(i*100, i*100+10); -- hm0闂撮殧100錛屾瘡孌?0涓彿鐮侊紝鏁呬笉浼氫氦鍙?br />
end loop;
end;
/
commit;
-- 寤虹儲寮?br />
create index i_test_1 on test(hm0, hm1);
銆愪綆鏁堟ā寮忋?br />
-- 鏌ユ壘鍙風爜 2000006 鏄惁鍦ㄥ彿鐮佹鍒楄〃涓?br />
select * from test a
where a.hm0 <= 2000006 and a.hm1>= 2000006
;
HM0 HM1
---------- ----------
2000000 2000010
-- 娉ㄦ剰鏌ヨ璁″垝涓殑 Search columns=1; 浣庢晥鐨勫師鍥犲湪浜嶰racle浼氬垽鏂?hm0 <= 2000006 鐨勬瘡鏉¤褰曟槸鍚︽弧瓚沖叏閮╳here鏉′歡
SELECT STATEMENT, GOAL = CHOOSE
INDEX RANGE SCAN Object owner=SCOTT Object name=I_TEST_1 Search columns=1
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
54 consistent gets -- 璁板綍鏁板澶氭椂錛岃鍊間細鍔犲ぇ
銆愰噸鏋勬柟妗堛?br />
-- 鍓嶆彁錛?br />
-- 1. 闇鍦?hm0 涓婂緩涓 desc 绱㈠紩
-- 2. 鍒╃敤 rownum<... 鐗規(guī)?璁㎡racle鎵懼埌絎竴鏉¤褰曞嵆鍋滄鎵弿
create index i_test_2 on test(hm0 desc);
-- 鍒╃敤琛ㄦ湰韜涔夊喅瀹氱殑鍙風爜孌典笉浼氫氦鍙夌殑鐗規(guī)э紝榪欎簺Oracle浼樺寲鍣ㄦ槸涓嶄細鐭ラ亾鐨? index hint浼間箮涓嶈兘灝?鍚﹀垯Oracle涓嶄細鑷姩璧拌繖涓儲寮?br />
select * from(
select /*+ index(a i_test_2) */ * from test a
where a.hm0 <= 2000006
order by a.hm0 desc) b
where rownum<2 and b.hm1 >= 2000006;
HM0 HM1
---------- ----------
2000000 2000010
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=3 Card=1 Bytes=26)
1 0 COUNT (STOPKEY)
2 1 VIEW (Cost=3 Card=1 Bytes=26)
3 2 TABLE ACCESS (BY INDEX ROWID) OF 'TEST' (Cost=3 Card=1
Bytes=26)
4 3 INDEX (RANGE SCAN) OF 'I_TEST_2' (NON-UNIQUE) (Cost=
2 Card=2)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
3 consistent gets
-- 緇撴潫嫻嬭瘯鍒犺〃
drop table test;
perl5鍘熷垱@20110430
]]>