The ORACLE String concatenation aggregate function can be used for group

The ORACLE String concatenation aggregate function can be used for group by 1. create type strcat_type www.2cto.com -- the essence of defining a type aggregate function is an object create or replace type strcat_type as object (cat_string varchar2 (4000), -- object initializes static function odciaggresponinitialize (cs_ctx In Out strcat_type) return number, -- Iteration Method of the aggregate function (this is the most important method) member function ODCIAggregateIterate (self In Out strcat_type, value in varchar2) return number, -- when the query statement is executed and handed In, this method can be applied to aggregate multiple running query results into member function ODCIAggregateMerge (self In Out strcat_type, ctx2 In Out strcat_type) return number, -- terminate the processing penalty of the collection function and return the result of the collection function processing penalty. member function odciaggresponterminate (self In Out strcat_type, returnValue Out varchar2, flags in number) return number) 2. build type body strcat_type www.2cto.com create or replace type body strcat_type is static function ODCIAggregateInitialize (cs_ctx in out strcat_type) return number is begin cs_ctx: = strcat_type (null); return ODCIConst. success; end; member function ODCIAggregateIterate (self in out strcat_type, value IN varchar2) return number is begin/* string already "", "respectively */self. cat_string: = self. cat_string | "", "" | value; return ODCIConst. success; end; member function odciaggresponterminate (self IN Out strcat_type, returnValue OUT varchar2, flags IN number) return number is begin/* remove null (is null) */returnValue: = ltrim (rtrim (self. cat_string, "", ""), "", ""); return ODCIConst. success; end; member function ODCIAggregateMerge (self in out strcat_type, ctx2 IN Out strcat_type) return number is begin self. cat_string: = self. cat_string | "", "" | ctx2.cat _ string; return ODCIConst. success; end; www.2cto.com 3. build FUNCTION func_strcat create or replace function func_strcat (input varchar2) RETURN varchar2 -- RETURN Value PARALLEL_ENABLE aggregate using strcat_type; -- accumulate parallel 4. result * t_test t; id keyword synonyms 1 coffee shop 2 coffee house 3 coffee shop 4 music popular music 5 music classical music 6 life livelihood comfortable living livelihood 7 life livelihood _________________________________ t. keyword, func_strcat (t. synonyms) t_test t group by t. keyword; keyword func_strcat (t. synonyms) coffee shops, coffee houses, coffee shops, and coffee shops for a comfortable life and livelihood, as well as popular music and classical music