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ORACLE字符集研究DextrysCo.,Ltd.KelsonCongDBATeam©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.2飞刀,又见飞刀什么是字符集字符集就是按照一定的字符编码方案,对一组特定的符号,分别赋予不同数值编码的集合。Oracle数据库最早支持的编码方案是US7ASCII。Oracle的字符集命名遵循以下命名规则:即:语言比特位数编码比如:ZHS16GBK表示采用GBK编码格式、16位(两个字节)简体中文字符集©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.3飞刀,又见飞刀字符编码方案单字节编码单字节7位字符集,可以定义128个字符,最常用的字符集为US7ASCII单字节8位字符集,可以定义256个字符,适合于欧洲大部分国家例如:WE8ISO8859P1(西欧、8位、ISO标准8859P1编码)©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.4飞刀,又见飞刀多字节编码变长多字节编码某些字符用一个字节表示,其它字符用两个或多个字符表示,变长多字节编码常用于对亚洲语言的支持,例如日语、汉语、印地语等例如:AL32UTF8(其中AL代表ALL,指适用于所有语言)、zhs16cgb231280©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.5飞刀,又见飞刀定长多字节编码每一个字符都使用固定长度字节的编码方案,目前oracle唯一支持的定长多字节编码是AF16UTF16,也是仅用于国家字符集©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.6飞刀,又见飞刀unicode编码Unicode是一个涵盖了目前全世界使用的所有已知字符的单一编码方案,也就是说Unicode为每一个字符提供唯一的编码。UTF-16是unicode的16位编码方式,是一种定长多字节编码,用2个字节表示一个unicode字符,AF16UTF16是UTF-16编码字符集。©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.7飞刀,又见飞刀UTF-8是unicode的8位编码方式,是一种变长多字节编码,这种编码可以用1、2、3个字节表示一个unicode字符,AL32UTF8,UTF8、UTFE是UTF-8编码字符集©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.8当一种字符集(字符集A)的编码数值包含所有另一种字符集(字符集B)的编码数值,并且两种字符集相同编码数值代表相同的字符时,则字符集A是字符集B的超级,或称字符集B是字符集A的子集。©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.9Oracle8i和oracle9i官方文档资料中备有子集-超级对照表(subset-supersetpairs),例如:WE8ISO8859P1是WE8MSWIN1252的子集。由于US7ASCII是最早的Oracle数据库编码格式,因此有许多字符集是US7ASCII的超集,例如WE8ISO8859P1、ZHS16CGB231280、ZHS16GBK都是US7ASCII的超集。©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.10大师的网站上提供的超集子集对照表©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.11查看字符集的工具:LBUILDER©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.12©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.13数据库字符集数据库字符集(oracle服务器端字符集)数据库字符集在创建数据库时指定,在创建后通常不能更改。在创建数据库时,可以指定字符集(CHARACTERSET)和国家字符集(NATIONALCHARACTERSET)。©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.14数据库字符集字符集用来存储CHAR,VARCHAR2,CLOB,LONG等类型数据用来标示诸如表名、列名以及PL/SQL变量等用来存储SQL和PL/SQL程序单元等©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.15数据库字符集国家字符集:用以存储NCHAR,NVARCHAR2,NCLOB等类型数据国家字符集实质上是为oracle选择的附加字符集,主要作用是为了增强oracle的字符处理能力,因为NCHAR数据类型可以提供对亚洲使用定长多字节编码的支持,而数据库字符集则不能。国家字符集在oracle9i中进行了重新定义,只能在unicode编码中的AF16UTF16和UTF8中选择,默认值是AF16UTF16©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.16数据库字符集讨论:1、什么情况下用CHAR,NCHAR?2、如何决定数据库字符集?©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.17数据库字符集可以查询以下数据字典或视图查看字符集设置情况nls_database_parameters、props$、v$nls_parameters查询结果中NLS_CHARACTERSET表示字符集,NLS_NCHAR_CHARACTERSET表示国家字符集©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.18数据库字符集©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.19数据库字符集如何修改服务器端字符集AlterdatabasecharactersetZHS16GBK此方法慎用!千万不要通过修改PROPS$的方式修改新的字符集一定是老字符集的超集©Copyright,SuzsoftCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved.©Copyright,DextrysCo.,Ltd.ConfidentialandProprietaryInformation.AllRightsReserved
本文标题:Oracle字符集研究
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