Oracle全文搜索中文

Oracle从7.3开始支持全文检索，即用户可以使用Oracle服务器的上下文（ConText）选项完成基于文本的查询。具体可以采用通配符查找、模糊匹配、相关分类、近似查找、条件加权和词意扩充等方法。在Oracle8.0.x中称为ConText ；在Oracle8i中称为interMedia Text ； Oracle9i以后称为Oracle Text。下面通过示例了解一下oracle全文检索。分派用户相应权限grant connect,resource to scott;
grant ctxapp to scott;
alter user portal default role all;
--对象权限
grant execute on ctx_ddl to scott; 解锁ctxsys用户
alter user ctxsys account unlock identified by ctxsys; 用应用用户登录,设置搜索器类型
SQL> conn scott/tiger;BEGIN
    ctx_ddl.create_preference （"main_lexer","CHINESE_LEXER"）;
    ctx_ddl.create_preference（"mywordlist", "BASIC_WORDLIST"）;
    ctx_ddl.set_attribute（"mywordlist","PREFIX_INDEX","TRUE"）;
    ctx_ddl.set_attribute（"mywordlist","PREFIX_MIN_LENGTH",1）;
    ctx_ddl.set_attribute（"mywordlist","PREFIX_MAX_LENGTH", 5）;
    ctx_ddl.set_attribute（"mywordlist","SUBSTRING_INDEX", "YES"）;
END;
/
这里说一下词法分析器（lexer），词法分析器有三种：
1）basic_lexer: 针对英语。它能根据空格和标点来将英语单词从句子中分离，还能自动将一些出现频率过高已经失去检索意义的单词作为‘垃圾’处理，如if , is 等，具有较高的处理效率。但只认空格和标点，而汉语的一句话中通常不会有空格，会把整句话作为一个组,事实上失去检索能力。
2）chinese_vgram_lexer: 专门的汉语分析器，支持所有汉字字符集（ZHS16CGB231280 ZHS16GBK ZHT32EUC ZHT16BIG5 ZHT32TRIS ZHT16MSWIN950 ZHT16HKSCS UTF8 ）。但分词方法太简单，每个组合都作为一个词，既占用空间又效率不高。
3）chinese_lexer: 这是一个新的汉语分析器，只支持utf8字符集。chinese_lexer的最大改进就是能认识大部分常用汉语词汇，因此能更有效率地分析句子。创建示例数据
create table docs（ id number, name varchar2（200）, address varchar2（2000））;
insert into docs values（1,"John Smith","Room 403,No.37,ShiFan Residential Quarter,BaoShan District"）;
insert into docs values（2,"Noah Abelard","Room 201,No.34,Lane 125,XiKang Road（South）,HongKou District"）;
insert into docs values（3,"Michael Cole","Room 42， Zhongzhou Road，Nanyang City， Henan Prov. "）;
insert into docs values（4,"Thomas Matthew","Hongyuan Hotel, Jingzhou city, Hubei Prov. "）;
insert into docs values（5,"Joseph","Special Steel Corp，No.272， Bayi Road，Nanyang City， Henan Prov. "）;
insert into docs values（6,"Lauren","Room 702, 7th Building, Hengda Garden, East District, Zhongshan "）;
insert into docs values（7,"Kevin Victoria","Room 601, No.34 Long Chang Li, Xiamen, Fujian "）;
insert into docs values（8,"Michael","Cheng Nuo Ban, Gong Jiao Zong Gong Si, Xiamen, Fujian "）;
insert into docs values（9,"Timothy Katherine","NO. 204,Entrance A, Building NO. 1, The 2nd Dormitory of the NO. 4 State-owned Textile Factory, 53 Kaiping Road, Qingdao, Shandong"）;
insert into docs values（10,"Zhou Wangcai","Room 601, No.34 Long Chang Li,Xiamen, Fujian, China 361012"）;
insert into docs values（11,"Sebastian Jared","Cheng Nuo Ban, Gong Jiao Zong Gong SiXiamen, Fujian, China 361004"）;
insert into docs values（12,"Jenna","NO. 204, A, Building NO. 1,The 2nd Dormitory of the NO. 4 State-owned Textile Factory,53 Kaiping Road, Qingdao,Shandong, China 266042 "）;
insert into docs values（13,"Catherine","Room403,No.37,SiFanResidentialQuarter,BaoShanDistrict"）;
insert into docs values（14,"Sebastian Cole","1 Team CaiQi ChuanXiBei Mining Area JiangYou City SiChuan Province China"）;
insert into docs values（15,"Timothy Jared ","Room 201,No.34,Lane 125,XiKang Road（South）,HongKou District"）;
insert into docs values（16,"张三","中国北京朝阳区北小营亚运花园1号楼8B"）;
insert into docs values（17,"李四","上海世纪大道1500号9楼"）;
insert into docs values（18,"王五","四川成都经济技术开发区世纪大道515号"）;
/对文本列建立文档CONTEXT索引，并且指定搜索器/过滤器/单词列表/
CREATE INDEX idx_docs_address ON docs（address）
indextype is ctxsys.context parameters
（"DATASTORE CTXSYS.DIRECT_DATASTORE FILTER CTXSYS.INSO_FILTER LEXER main_lexer WORDLIST mywordlist"）;

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