SQL Server 2019

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create table Parametre (PAR_ID int, PAR_NOM varchar(50), PAR_TYPE varchar(50))
insert into Parametre values (1, 'code_po', 'string'), (2, 'REF_SO', null), (3, 'NB_AR', null)
3 rows affected

select * from Parametre


PAR_ID
PAR_NOM
PAR_TYPE


1
code_po
string

2
REF_SO
null

3
NB_AR
null


select case when p.PAR_TYPE is not null then p.PAR_NOM else null end as INPUT,
       case when p.PAR_TYPE is null then p.PAR_NOM else null end as OUTPUT,
       p.PAR_TYPE
from   Parametre p
  


INPUT
OUTPUT
PAR_TYPE


code_po
null
string

null
REF_SO
null

null
NB_AR
null