PostgreSQL选择最新的不同记录

Question

我有一个类似于这样的表：

id  fkey  srno  remark  date
1   A001  1
2   A001  2
3   A002  1
4   A003  1 
5   A002  2

我希望你能够根据最大SRNO基于不同的最新记录，就像这样。

2  A001  2
4  A003  1
5  A002  2

- Kuldeep Thakur

Answer 1

在Postgres中实现这一点的最佳方法是使用DISTINCT ON：

SELECT DISTINCT ON (fkey) id, fkey, srno
FROM yourTable
ORDER BY fkey, srno DESC;

演示

注：以上内容涉及IT技术。

- Tim Biegeleisen

Answer 2

使用窗口函数 row_number()

select * from (
select *,row_number() over(PARTITION by fkey order by srno desc) rn from table1 t1 
) t where rn=1

您可以使用CTE编写它

with cte as
(
    select *,row_number() over(PARTITION by fkey order by srno desc) rn from 
    table_name t1
) select * from cte where rn=1

- Zaynul Abadin Tuhin

Answer 3

你可以使用相关子查询

select * from tablename where srno in
(select max(srno) from tablename b where a.fkey=b.fkey)

- Fahmi

Answer 4

您可以使用带有IN运算符的子查询

with tab(id, fkey, srno) as 
(
 select 1,'A001',1 union all
 select 2,'A001',2 union all    
 select 3,'A002',1 union all
 select 4,'A003',1 union all    
 select 5,'A002',2   
)
select *
  from tab
 where ( fkey, srno ) in
 (
  select fkey, max(srno)
    from tab
   group by fkey
 );

id  fkey    srno
2   A001     2
4   A003     1
5   A002     2

Rextester演示

- Barbaros Özhan