Question

tryng to select table rows and then use subqueries to generate single row list (item1,item2,item3)

anyway sql:

select 
  username,
  concat(firstname || ' ', lastname) as name,
  email,
  phone,
  (
  select 
    ltrim(sys_connect_by_path(res, ', '), ', ')
  from (
    select 
      count(*) over() as cnt, 
      row_number() over(order by ofield) as rnum, 
      (select name from rooms where code=roomcode) as res 
    from adminrooms
    where roomcode=admins.code) /*admins.code - come from main query but it gives error: invalid identifier*/
  where cnt=rnum start with rnum=1 connect by prior rnum=(rnum-1)
  ) as groups
from admins
where frozen=0 and (type <> 'root' or type is null)

problem seems to be the main query field ‘code’ from table ‘admins’ don’t work inside list generation query

Answer 1

Based on your db diagram, the best way to do it is to use a custom string aggregation function and then just do a group by. This is similar to mysql group_concat.

If you make a function called string_agg() using the above link, you can use it as below in your code:

select a.username, string_agg(c.name) from admins a, adminrooms b, groups c
where a.code=b.admincode
and b.groupcode=c.code
group by a.username

Here is the string_agg function create script. Just run this as a script and you will have the function above (taken from the link shown above):

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