????????????????
????1??IN ??????
??????INд??????SQL?????????????д??????????????????????????????????????IN??SQL???????????????Oracle??е????????????IN??SQL????IN??SQL??????????
????ORACLE????????????????????????????????????????IN????????????????????????????????????????????????????????????????IN??SQL???????????????????????SQL??????????????????????з???????????SQL??????????
???????????????????????SQL???о?????????IN??????????EXISTS ???????檔
????2??NOT IN??????
?????????????в?????????????????????????????
???????????????NOT EXISTS ????????
????3??IS NULL ??IS NOT NULL???????ж???????????
?????ж????????????????????????????????????????????????
????????????????????????????????????棬?磺a is not null ??? a>0 ??a>’’??????????????????????????????????????????????β????????????????
????4??> ?? < ?????????????С?????????
?????????С??????????????????????????????????????????????????????е??????????????????????????????100?????????????????A??30??????A=0??30??????A=1??39??????A=2??1??????A=3????????A>2??A>=3??Ч???к?????????????A>2?ORACLE????????2????????????б?????A>=3?ORACLE????????=3??????????
????5??LIKE??????
????LIKE??????????????????????????????????????????????????????????????ò??????????????????????LIKE ‘%5400%’ ??????????????????????LIKE ‘X5400%’??????÷?Χ??????
?????????????????YW_YHJBQK?????????????????????????????? YY_BH LIKE ‘%5400%’ ?????????????????裬??????YY_BH LIKE ’X5400%’ OR YY_BH LIKE ’B5400%’ ???????YY_BH????????????????Χ???????????????????
????6??UNION??????
????UNION????б????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????UNION???磺
????select * from gc_dfys
????union
????select * from ls_jg_dfys
???????SQL????????????????????????????????????????????????????????????????????????????????????????????????
?????????????????UNION ALL?????????UNION?????UNION ALL??????????????????????????
????select * from gc_dfys
????union all
????select * from ls_jg_dfys
????????SQL??д?????
????1????????????????д??SQL?????
?????????SQL??A?????д??? Select * from zl_yhjbqk
????B?????д??? Select * from dlyx.zl_yhjbqk?????????????????
????C?????д??? Select * from DLYX.ZLYHJBQK????д??????
????D?????д??? Select * from DLYX.ZLYHJBQK???м??????
???????????SQL??ORACLE??????????????????????е?????????????????ORACLE???????SGA??????????ó?ORACLE?????SQL ????????????η???????????ù?????棬?????SQL????????????д????????????ORACLE????????Σ??????????????????ε???????????????????????SQL???????????????????????????????ORACLE??????????SQL?????????
????2??WHERE???????????????
????WHERE????????????????????????????????????????磺
????Select * from zl_yhjbqk where dy_dj = '1KV????' and xh_bz=1
????Select * from zl_yhjbqk where xh_bz=1 and dy_dj = '1KV????'
????????????SQL??dy_dj????????????xh_bz?????????????????ζ??????????????????е???????????裬?????SQL??dy_dj = '1KV????'????????????????99%????xh_bz=1???????0.5%??????е????SQL?????99%???????????dy_dj??xh_bz???????????е????SQL?????0.5%???????????dy_dj??xh_bz???????????ó??????SQL??CPU?????????????????
????3??????????????
??????FROM???????е??б??????SQL?????????????????????ORACLE??ж?????????????????￡?ORACLE??????????????????????????????????????????????????????????檔????????????????????????ORACLE????????С????????????д????????