select json_object(key 'x1' value 0.0133, key 'x2' value 0.133) from dual t

{"x1":.0133,"x2":0.133}

with c as
 (select  systimestamp ct_change  from dual 
 --union all select to_timestamp('10-Sep-02 14:10:10.123000', 'DD-Mon-RR HH24:MI:SS.FF') from dual
 )
select 
       json_object(key 'ct_change' value c.ct_change)
  from c 

with c as
 (select to_number('-0.' || lpad('9', 39, '9'), '9D' || lpad('9', 39, '9')) cn_value from dual)
select cn_value, json_object(key 'ct_change' value cn_value) from c

with
  w_data as
  (
    select --+materialize
           *
      from (select 1 as f, sysdate as d1, sysdate + 100 as d2 from dual)
  ),
  w_tree as
  (
    select 1 as f, to_number(null) as pf, 1    as cf from dual union all
    select 2 as f, to_number(1)    as pf, null as cf from dual union all
    select 3 as f, to_number(1)    as pf, null as cf from dual union all
    select 4 as f, to_number(1)    as pf, null as cf from dual union all
    select 5 as f, to_number(null) as pf, 1    as cf from dual union all
    select 6 as f, to_number(5)    as pf, null as cf from dual union all
    select 7 as f, to_number(5)    as pf, null as cf from dual union all
    select 8 as f, to_number(7)    as pf, null as cf from dual
  )
select 1
  from w_tree t
       left join w_data d
              on connect_by_root(cf) = d.f
start with t.cf =1
connect by prior t.f = t.pf