??????Oracle?????????У?????????????????????????????????????Щ?????м????????????????ν?????????????????????????????????????????????????????

????????????????????????????

????????Instance???????????all_rows????

?????????????????????????

?????????С?????????????Oracle???????????????????????

?????????????

???????????init.ora?е?OPTIMIZER_MODE????????????????Rule??Choose???????????????????4???????Hint??

?????????????????????

????1????????????????????ν???δ???????????????У?????????INDEX SKIP SCAN???

????2?????????null???table???????????????????select count??*?? from table??????????????

????3??????????????ú???????????????????????????????????????????????

????4?????????????н??????????????????????????????磺select * from t where indexed_column = 5????indexed_column?н????????????????????????Oracle??????????????????????????????????select * from t where to_number??indexed_column?? = 5????????????????????????case3?????????????????????磺 select * from t where trunc??date_col?? = trunc??sysdate??????date_col??????У?????д???????????????д??select * from t where date_col >= trunc??sysdate?? and date_col < trunc??sysdate+1??????????????????

????5??????????????????????????????????full scan table ?????????????????????????????????????????????full scan table??????????????Oracle???????????????????????????????????????????????????????????????????????

????6??<>

????7??like’%dd’?????????

????????Oracle??м???????????????????????????????????????????ε??????????????????