update table1 set name1 = (case when name1 is null then null else 'boy'),
name2 = (case when name2 is null then null else 'boy'),
name3 = (case when name3 is null then null else 'boy'),
name4 = (case when name4 is null then null else 'boy')
where id = 3
name2=(case when name2 is not null then 'boy' end),
name3=(case when name3 is not null then 'boy' end),
name4=(case when name4 is not null then 'boy' end)
where id=3