SQL 列转行/list agg 列超长处理方法

CREATE USER tester IDENTIFIED BY tester ;
grant   dba,resource,connect to tester;   
conn tester/tester


create table t24(num number,a varchar2(30));
begin
for i in 1.. 1000
loop
insert into t24 values(1,'aaaa');


end loop;
commit;
end;
/
select num,string_agg(a) from t24 group by num  ;




  
CREATE OR REPLACE TYPE t_string_agg AS OBJECT
(
  g_string  VARCHAR2(32767),


  STATIC FUNCTION ODCIAggregateInitialize(sctx  IN OUT  t_string_agg)
    RETURN NUMBER,


  MEMBER FUNCTION ODCIAggregateIterate(self   IN OUT  t_string_agg,
                                       value  IN      VARCHAR2 )
     RETURN NUMBER,


  MEMBER FUNCTION ODCIAggregateTerminate(self         IN   t_string_agg,
                                         returnValue  OUT  VARCHAR2,
                                         flags        IN   NUMBER)
    RETURN NUMBER,


  MEMBER FUNCTION ODCIAggregateMerge(self  IN OUT  t_string_agg,
                                     ctx2  IN      t_string_agg)
    RETURN NUMBER
);
/
SHOW ERRORS




CREATE OR REPLACE TYPE BODY t_string_agg IS
  STATIC FUNCTION ODCIAggregateInitialize(sctx  IN OUT  t_string_agg)
    RETURN NUMBER IS
  BEGIN
    sctx := t_string_agg(NULL);
    RETURN ODCIConst.Success;
  END;


  MEMBER FUNCTION ODCIAggregateIterate(self   IN OUT  t_string_agg,
                                       value  IN      VARCHAR2 )
    RETURN NUMBER IS
  BEGIN
    SELF.g_string := self.g_string || '||''|''||' || value;
    RETURN ODCIConst.Success;
  END;


  MEMBER FUNCTION ODCIAggregateTerminate(self         IN   t_string_agg,
                                         returnValue  OUT  VARCHAR2,
                                         flags        IN   NUMBER)
    RETURN NUMBER IS
  BEGIN
    returnValue := RTRIM(LTRIM(SELF.g_string, '||''|''||'), '||''|''||');
    RETURN ODCIConst.Success;
  END;


  MEMBER FUNCTION ODCIAggregateMerge(self  IN OUT  t_string_agg,
                                     ctx2  IN      t_string_agg)
    RETURN NUMBER IS
  BEGIN
    SELF.g_string := SELF.g_string || '||''|''||' || ctx2.g_string;
    RETURN ODCIConst.Success;
  END;
END;
/
SHOW ERRORS




CREATE OR REPLACE FUNCTION string_agg (p_input VARCHAR2)
RETURN VARCHAR2
PARALLEL_ENABLE AGGREGATE USING t_string_agg;
/
SHOW ERRORS


SELECT num, LISTAGG(a, ',') WITHIN GROUP (ORDER BY a) AS ll FROM   t24 GROUP BY num;




select num,
       to_clob(ltrim(MAX(sys_connect_by_path(a, '||''|''||')) KEEP(dense_rank last order by num), '||''|''||'))
  from (select num,
               row_number() OVER(PARTITION BY num ORDER BY a) curr,
               row_number() OVER(PARTITION BY num ORDER BY a) - 1 prev,
               a
          from t24)
 group by num
connect by prev = prior curr
       and num = prior num
 start with curr = 1;


 
 tester@RAC11G>SELECT num, LISTAGG(a, ',') WITHIN GROUP (ORDER BY a) AS ll FROM   t24 GROUP BY num;
SELECT num, LISTAGG(a, ',') WITHIN GROUP (ORDER BY a) AS ll FROM   t24 GROUP BY num
                                                                   *
ERROR at line 1:
ORA-01489: result of string concatenation is too long


tester@RAC11G>select num,
       to_clob(ltrim(MAX(sys_connect_by_path(a, '||''|''||')) KEEP(dense_rank last order by num), '||''|''||'))
  3    from (select num,
  4                 row_number() OVER(PARTITION BY num ORDER BY a) curr,
  5                 row_number() OVER(PARTITION BY num ORDER BY a) - 1 prev,
               a
          from t24)
  8   group by num
  9  connect by prev = prior curr
 10         and num = prior num
 11   start with curr = 1;
ERROR:
ORA-01489: result of string concatenation is too long

no rows selected

解决方案很朴实 ~

如下

create table test as select lpad('a',8000,'a') a from dual;
select dbms_utility.get_hash_value( a||'_'||a,0,1073741824) from test;
select  a||'_'||a  from test;
alter table test add c varchar2(4000);
update test set c=  lpad('a',8000,'a');
commit;
set serveroutput on
declare 
aa varchar2(32767);
cc varchar2(32767);
begin
select a,c into aa,cc from test;
--aa :=aa||lpad('a',8000,'a');
dbms_output.put_line(dbms_utility.get_hash_value(aa||'0'||cc,0,1073741824));
dbms_output.put_line(dbms_utility.get_hash_value(aa||'1'||cc,0,1073741824));
dbms_output.put_line(dbms_utility.get_hash_value( lpad('a',3999,'a'),0,1073741824));
end;
/
105111839
622607691
621653836