???????????????ACID
????Atomicity:?????
????Consistency:?????
????Isolation:??????
????Duration:?????
??????SQL????ж???????????????????
????1??read uncommitted  δ????
?????????е???????????????????????????????????????????????δ?????????????????????
????2??read committed       ????
???????????????????????oracle?????????????MySQL?????????????
?????????????壺??????????????????“????”?????????????????????
???????仰??????????????????????????????????????????????????????
????3??repeatable read       ???????
????????????????????д????????????????д??????????????????????MySQL???????????
????4??serializable          ????л?
??????????????Serializable??????????????????????????????????′????????????????????