Oracle 11g Release 2

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BANNER
Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE 11.2.0.2.0 Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

with tab(db, dbms, inst, "schema", "table", "column", hdft, N_Identity, "class" ) as 
(
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',   null    ,  null, 'HIGH' from dual union all
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'GID'    ,  null, null   from dual union all
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'Phone'  ,  null, null   from dual union all 
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'Account',  null, null   from dual union all  
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'Visa'   ,  null, null   from dual union all  
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'Mail'   ,  null, null   from dual union all  
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'Email'  ,  null, null   from dual union all  
    select 'IDS', 'TD',   'SBD',    'IDS',   'Data_Val',  'cust_t',  'Login'  , 'Yes', null   from dual union all
    select 'TDS', 'TD',   'FDT',    'TDS',   'Expense' ,  'Exp_t' ,  'Name'   ,  null, 'LOW'  from dual union all
    select 'TDS', 'TD',   'FDT',    'TDS',   'Expense' ,  'Exp_t' ,   null    , 'Yes', null   from dual
), tab2 as
(    
select db, dbms, inst, "schema", "table", "column", hdft,
       first_value("class") over (partition by db) as "class", 
       nvl(N_Identity,'Yes') as N_Identity 
  from tab                    
)
select * from tab2 where hdft is not null

DB	DBMS	INST	schema	table	column	HDFT	class	N_IDENTITY
IDS	TD	SBD	IDS	Data_Val	cust_t	GID	HIGH	Yes
IDS	TD	SBD	IDS	Data_Val	cust_t	Phone	HIGH	Yes
IDS	TD	SBD	IDS	Data_Val	cust_t	Account	HIGH	Yes
IDS	TD	SBD	IDS	Data_Val	cust_t	Visa	HIGH	Yes
IDS	TD	SBD	IDS	Data_Val	cust_t	Login	HIGH	Yes
IDS	TD	SBD	IDS	Data_Val	cust_t	Mail	HIGH	Yes
IDS	TD	SBD	IDS	Data_Val	cust_t	Email	HIGH	Yes
TDS	TD	FDT	TDS	Expense	Exp_t	Name	LOW	Yes