从列表获取自定义不同值

Question

Table data and expected data as below

I wanted to select the distinct ID and Name, irrespective of branch. But I want the branch name to be displayed. If branch need not be displayed I can use substring. Can the result be achieved using CTE.

Answer 1

As you don't appear to care about which 'branch' needs to be returned, you can simply use a row_number within a CTE to return just one result per ID value:

declare @t table(ID int,Name varchar(20));
insert into @t values
 (10,'Manoj (CS)')
,(10,'Manoj (IS)')
,(20,'Ajay (CS)')
,(20,'AJAY (IS)')
,(30,'Sunjay(EC)')
,(40,'Lina(IS)')
,(40,'Lina(CS)')
,(40,'Lina(EC)')
,(50,'Mary(IS)')
,(50,'Mary(EC)');

with d as
(
    select ID
        ,Name
        ,row_number() over (partition by ID order by Name) as rn
    from @t
)
select ID
        ,Name
from d
where rn = 1;

Output:

+----+------------+
| ID |    Name    |
+----+------------+
| 10 | Manoj (CS) |
| 20 | Ajay (CS)  |
| 30 | Sunjay(EC) |
| 40 | Lina(CS)   |
| 50 | Mary(EC)   |
+----+------------+

---

If you do have a preference for the (CS) branch however, you would need to alter the row_number slightly:

with d as
(
    select ID
        ,Name
        ,row_number() over (partition by ID
                            order by case when right(Name,4) = '(CS)'
                                          then 1
                                          else 2
                                          end
                                    ,Name
                            ) as rn
    from @t
)
select ID
        ,Name
from d
where rn = 1;

Answer 2

You can use row_number() function with TIES :

select top (1) with ties *
from table t
order by row_number() over (partition by id order by name);

Answer 3

As mentioned in the comments: Change your datamodel.

If you must live with the table as is, all you want is: all student IDs, each with one branhc/subject name arbitrarily picked. This can be achieved with a simple aggregation:

select id, min(name) from mytable group by id;