Question

This is master table Query

Select * 
from AC_TAB 
where AC_ID = 7 ; 

AC_PK AC_ID TYPE  STATUS   INS_DATE               VALID
102   7     0     0        3/21/2012 3:35:08 PM   0 
103   7     1     0        3/21/2012 3:35:08 PM 
104   7     2     1        3/21/2012 3:35:08 PM 

I am joining this table with txn table using ac_id. Since here its having 3 rows for ac_id 7 , my txn table returning 3 times. how to restrict this. since i want to return only one irrespective of type

MY Txn Query

Select txn_id, amount 
from txn_hdr , ac_tab 
where txn_ac_id = ac_id ;

txn_id  amount   
 1       200 
 1       200 
 3       100 
 3       100 

Answer 1

It is not actually clear what you need but it sounds like you only want to return one record per ac_id from the AC_TAB. If so, then there are a few ways that you can do this.

Using a subquery:

select *
from
(
  select max(INS_DATE) INS_DATE, AC_ID
  from ac_tab
  group by AC_ID
) a
inner join txn_hdr t
  on a.ac_id = t.ac_id;

Or with CTE using a row_number():

;with cte as
(
  select a.ins_date, a.ac_id, t.amount, row_number() 
            over(partition by a.ac_id order by a.ins_date desc) rn
  from ac_tab a
  inner join txn_hdr t
    on a.ac_id = t.ac_id
)
select *
from cte 
where rn = 1;

Or with a row_number() in a subquery:

select *
from 
(
  select a.ins_date, a.ac_id, t.amount, row_number() 
            over(partition by a.ac_id order by a.ins_date desc) rn
  from ac_tab a
  inner join txn_hdr t
    on a.ac_id = t.ac_id
) x
where rn = 1