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[每日一题] OCP1z0-047 :2013-08-10 INTERVAL DAY TO SECOND........................................

2013-08-10 23:52 796 查看

转载请注明出处：http://blog.csdn.net/guoyjoe/article/details/9887591

正解答案是：B引用akagea同学的解释http://www.itpub.net/thread-1808740-1-1.html“根据题意要求，需要存储的是一个时间间隔的数据，且方便加减，所以首先排除timestamp类型。然后题目要求最大的周期是30天，所以yeartomonth排除，因为该项只能精确到月。然后就剩下B“官方文档解释：

INTERVALYEARTOMONTHDatatype

INTERVAL

YEAR

TO

MONTH

storesaperiodoftimeusingthe

YEAR

and

MONTH

datetimefields.Thisdatatypeisusefulforrepresentingthedifferencebetweentwodatetimevalueswhenonlytheyearandmonthvaluesaresignificant.
Specify

INTERVAL

YEAR

TO

MONTH

asfollows:

INTERVALYEAR[(year_precision)]TOMONTH

DatetimeandIntervalExamples

Thefollowingexampleshowshowtodeclaresomedatetimeandintervaldatatypes.

hr@MYDB>hr@MYDB>SELECTlast_name,sysdate,hire_date,EXTRACT(YEARFROM(SYSDATE-hire_date)YEARTOMONTH)2||'years'3||EXTRACT(MONTHFROM(SYSDATE-hire_date)YEARTOMONTH)4||'months'"Interval"5FROMemployees;LAST_NAMESYSDATEHIRE_DATEInterval---------------------------------------------------------------------------------------------------Dilly10-AUG-1313-AUG-058years0monthsGates10-AUG-1311-JUL-067years1monthsPerkins10-AUG-1319-DEC-075years8monthsBell10-AUG-1304-FEB-049years6months中间结果省略Bull10-AUG-1320-FEB-058years6monthsDellinger10-AUG-1324-JUN-067years2monthsCabrio10-AUG-1307-FEB-076years6monthsChung10-AUG-1314-JUN-058years2months107rowsselected.

INTERVALDAYTOSECONDDatatype

INTERVAL

DAY

TO

SECOND

storesaperiodoftimeintermsofdays,hours,minutes,andseconds.Thisdatatypeisusefulforrepresentingtheprecisedifferencebetweentwodatetimevalues.
Specifythisdatatypeasfollows:

INTERVALDAY[(day_precision)]

TOSECOND[(fractional_seconds_precision)]

TIMESTAMPWITHTIMEZONEDatatype

TIMESTAMP

WITH

TIME

ZONE

isavariantof

TIMESTAMP

thatincludesatimezoneoffsetinitsvalue.Thetimezoneoffsetisthedifference(inhoursandminutes)betweenlocaltimeandUTC(CoordinatedUniversalTime—formerlyGreenwichMeanTime).Thisdatatypeisusefulforcollectingandevaluatingdateinformationacrossgeographicregions.
Specifythe

TIMESTAMP

WITH

TIME

ZONE

datatypeasfollows:

TIMESTAMP[(fractional_seconds_precision)]WITHTIMEZONE

oe@MYDB>colORDER_DATEfora30oe@MYDB>colIntervalfora30oe@MYDB>SELECTorder_id,sysdate,order_date,2EXTRACT(DAYFROM(SYSDATE-order_date)DAYTOSECOND)3||'days'4||EXTRACT(HOURFROM(SYSDATE-order_date)DAYTOSECOND)5||'hours'"Interval"6FROMorders;ORDER_IDSYSDATEORDER_DATEInterval----------------------------------------------------------------------------------244210-AUG-1328-JUL-9002.22.59.662632AM8414days21hours244310-AUG-1328-JUL-9003.34.16.562632AM8414days20hours244510-AUG-1328-JUL-9005.34.38.362632AM8414days18hours241810-AUG-1321-MAR-9608.18.21.862632AM6351days15hours241510-AUG-1330-MAR-9705.34.50.545196AM5977days18hours235710-AUG-1309-JAN-9812.19.44.123456PM5692days11hours省略中间结果244710-AUG-1327-JUL-0010.59.10.223344PM4762days0hours244110-AUG-1302-AUG-0001.22.48.734526AM4756days22hours1310-AUG-1304-AUG-1309.32.52.000000PM6days2hours13010-AUG-1304-AUG-1310.55.36.000000PM6days0hours107rowsselected.

TIMESTAMPWITHLOCALTIMEZONEDatatype

TIMESTAMP

WITH

LOCAL

TIME

ZONE

isanothervariantof

TIMESTAMP

thatincludesatimezoneoffsetinitsvalue.Itdiffersfrom

TIMESTAMP

WITH

TIME

ZONE

inthatdatastoredinthedatabaseisnormalizedtothedatabasetimezone,andthetimezoneoffsetisnotstoredaspartofthecolumndata.Whenauserretrievesthedata,Oraclereturnsitintheuser'slocalsessiontimezone.Thetimezoneoffsetisthedifference(inhoursandminutes)betweenlocaltimeandUTC(CoordinatedUniversalTime—formerlyGreenwichMeanTime).Thisdatatypeisusefulfordisplayingdateinformationinthetimezoneoftheclientsysteminatwo-tierapplication.
Specifythe

TIMESTAMP

WITH

LOCAL

TIME

ZONE

datatypeasfollows:

TIMESTAMP[(fractional_seconds_precision)]WITHLOCALTIMEZONE

timestampwithlocaltimezone和timesatampwithtimezone的最大区别就是，前者在用户提交时间给数据库的时，该类型会转换成数据库的时区来保存数据，即数据库保存的时间是数据库本地时区，当别的用户访问数据库时oracle会自动将该时间转换成当前客户端的时间。

实验：1、创建表gyj@MYDB>CREATETABLETIME_TEST(2TIMEDATE,3TIMESTPTIMESTAMP(3),4TIMESTP_TZTIMESTAMP(3)WITHTIMEZONE,5TIMESTP_LTZTIMESTAMP(3)WITHLOCALTIMEZONE);Tablecreated.
2、插入数据gyj@MYDB>INSERTINTOTIME_TESTVALUES(SYSDATE,SYSDATE,SYSDATE,SYSDATE);1rowcreated.gyj@MYDB>commit;Commitcomplete.
3、查询dbtimezone和sessiontimezone的值gyj@MYDB>selectdbtimezone,sessiontimezonefromdual;DBTIMESESSIONTIMEZONE-----------------------------------------------------------------+08:00+08:00
4、查看数据的值gyj@MYDB>colTIMESTPfora30gyj@MYDB>colTIMESTP_TZfora35gyj@MYDB>colTIMESTP_LTZfora30gyj@MYDB>SELECT*FROMTIME_TEST;TIMETIMESTPTIMESTP_TZTIMESTP_LTZ-----------------------------------------------------------------------------------------------------------10-AUG-1310-AUG-1311.09.16.000PM10-AUG-1311.09.16.000PM+08:0010-AUG-1311.09.16.000PM
5、修改会话的time_zone值gyj@MYDB>altersessionsettime_zone='+11:00';Sessionaltered.

6、查看结果gyj@MYDB>SELECT*FROMTIME_TEST;TIMETIMESTPTIMESTP_TZTIMESTP_LTZ-----------------------------------------------------------------------------------------------------------10-AUG-1310-AUG-1311.09.16.000PM10-AUG-1311.09.16.000PM+08:0011-AUG-1302.09.16.000AM
从上面的实验可以看出二者的去区别，当session的时区由8变为11是，时间增加三个小时别外可以参考这篇文章：http://space.itpub.net/9765498/viewspace-539881
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