TruncFunction(withdates)InOracle/PLSQL,thetruncfunctionreturnsadatetruncatedtoaspecificunitofmeasure.oracle中,trunc函数返回一个按照特定计量单位截取后的date值Thesyntaxforthetruncfunctionis:语法如下:trunc(dat1e,[format])da1teisthedatetotruncate.da1te是要截断的dateformatistheunitofmeasuretoapplyfortruncating.Iftheformatparameterisomitted,thetruncfunctionwilltruncatethedatetothedayvalue,sothatanyhours,minutes,orsecondswillbetruncatedoff.format是截取时依据的计量单位(类似于数字中的精度)。如果format省略,date1就返回当天的日期值,即只保留日期,时间为0:00:00Belowarethevalidformatparameters:以下是合法的参数值:UnitValidformatparametersYear】SYYYY,YYYY,YEAR,SYEAR,YYY,YY,YISOYear】IYYY,IY,IQuarter】QMonth】MONTH,MON,MM,RMWeek】WWIW】IWW】WDay】DDD,DD,JStartdayoftheweek】DAY,DY,DHour】HH,HH12,HH24Minute】MIAppliesTo:Oracle8i,Oracle9i,Oracle10g,Oracle11gForexample:trunc(to_date(\'22-AUG-03\'),\'YEAR\')wouldreturn\'01-JAN-03\'trunc(to_date(\'22-AUG-03\'),\'Q\')wouldreturn\'01-JUL-03\'trunc(to_date(\'22-AUG-03\'),\'MONTH\')wouldreturn\'01-AUG-03\'trunc(to_date(\'22-AUG-03\'),\'DDD\')wouldreturn\'22-AUG-03\'trunc(to_date(\'22-AUG-03\'),\'DAY\')wouldreturn\'17-AUG-03\'
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