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Oracle 函数replace和translate的比较

2009-06-02 15:40 471 查看

今天看了SQLCOOKBOOK中的一个例子，其中看到了两个函数Replace和Translate时产生了疑惑，感觉这两个函数的作用是一样的，书上面的例子也看的不是很明白，Google了一下，看了Oracle的官方解释，终于彻底明白了。官方的解释如下：

REPLACE

Descriptionoftheillustrationreplace.gif

Purpose

REPLACE

returns

char

witheveryoccurrenceof

search_string

replacedwith

replacement_string

.If

replacement_string

isomittedornull,thenalloccurrencesof

search_string

areremoved.If

search_string

isnull,then

char

isreturned.

Both

search_string

and

replacement_string

,aswellas

char

,canbeanyofthedatatypes

CHAR

VARCHAR2

NCHAR

NVARCHAR2

CLOB

,or

NCLOB

.Thestringreturnedisinthesamecharactersetas

char

.Thefunctionreturns

VARCHAR2

ifthefirstargumentisnotaLOBandreturns

CLOB

ifthefirstargumentisaLOB.

REPLACE

providesfunctionalityrelatedtothatprovidedbythe

TRANSLATE

function.

TRANSLATE

providessingle-character,one-to-onesubstitution.

REPLACE

letsyousubstituteonestringforanotheraswellastoremovecharacterstrings.

SeeAlso:

TRANSLATE

Examples
Thefollowingexamplereplacesoccurrencesof

with

BL

SELECTREPLACE('JACKandJUE','J','BL')"Changes"

FROMDUAL;

Changes

--------------

BLACKandBLUE

Translate




Descriptionoftheillustrationtranslate.gif

Purpose

[code]TRANSLATE

returns

expr

withalloccurrencesofeachcharacterin

from_string

replacedbyitscorrespondingcharacterin

to_string

.Charactersin

expr

thatarenotin

from_string

arenotreplaced.If

expr

isacharacterstring,thenyoumustencloseitinsinglequotationmarks.Theargument

from_string

cancontainmorecharactersthan

to_string

.Inthiscase,theextracharactersattheendof

from_string

havenocorrespondingcharactersin

to_string

.Iftheseextracharactersappearin

char

,thentheyareremovedfromthereturnvalue.
[/code]

Youcannotuseanemptystringfor[code]to_string

toremoveallcharactersin

from_string

fromthereturnvalue.OracleDatabaseinterpretstheemptystringasnull,andifthisfunctionhasanullargument,thenitreturnsnull.
[/code]

[code]TRANSLATE

providesfunctionalityrelatedtothatprovidedbythe

REPLACE

function.

REPLACE

letsyousubstituteasinglestringforanothersinglestring,aswellasremovecharacterstrings.

TRANSLATE

letsyoumakeseveralsingle-character,one-to-onesubstitutionsinoneoperation.
[/code]

Thisfunctiondoesnotsupport[code]CLOB

datadirectly.However,

CLOB

scanbepassedinasargumentsthroughimplicitdataconversion.
[/code]

SeeAlso:

"DatatypeComparisonRules"

formoreinformationand
REPLACE

Examples

Thefollowingstatementtranslatesabooktitleintoastringthatcouldbeused(forexample)asafilename.The[code]from_string

containsfourcharacters:aspace,asterisk,slash,andapostrophe(withanextraapostropheastheescapecharacter).The

to_string

containsonlythreeunderscores.Thisleavesthefourthcharacterinthe

from_string

withoutacorrespondingreplacement,soapostrophesaredroppedfromthereturnedvalue.
[/code]

SELECTTRANSLATE('SQL*PlusUser''sGuide','*/''','___')FROMDUAL;

TRANSLATE('SQL*PLUSU

--------------------

SQL_Plus_Users_Guide

selecttranslate('liyan4h123ui','#liyanhui','#')fromdual

结果：4123

selecttranslate('asadad434323','#0123456789','#')fromdual

结果：asadad

selectTRANSLATE('kkaxksx','kx','12')fromdual

结果：11a21s2

SQLCookBook上這個例子分解

selecttranslate('SMITH20','0123456789','##########')fromdual將

'SMITH20'
字符串中，所有數字替換為‘#’

結果是
'SMITH##'

selectreplace(translate('SMITH20','0123456789','##########'),'#','')fromdual將

'SMITH##'
中的'#'替換為''

結果是'SMITH'

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