SQL Server 2019

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create table t(id int primary key,v varchar(10));
insert into t (id,v)
values (3,'a'), (5,'b');
2 rows affected

select * from t


id
v


3
a

5
b


update t
set id = case when id = 3 then 5 else 3 end
where id in (3, 5);
2 rows affected

select * from t


id
v


3
b

5
a