Oracle??м??????????????????
???????????? ???????[ 2012/11/23 10:45:57 ] ????????
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????????Instance???????????all_rows????
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???????????init.ora?е?OPTIMIZER_MODE????????????????Rule??Choose???????????????????4???????Hint??
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????1????????????????????ν???δ???????????????У?????????INDEX SKIP SCAN???
????2?????????null???table???????????????????select count??*?? from table??????????????
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????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???????????????????????????????????????????????????????????????????????
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????7??like’%dd’?????????
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