My solution is:

declare @test-2 table(col1 int,col2 varchar(8))

insert into @test-2 values(1,'aaaa')

insert into @test-2 values(2,'delbbbb')

insert into @test-2 values(3,'delcccc')

insert into @test-2 values(4,NULL)

insert into @test-2 values(5,'dddd')

select col1 from @test-2 where COALESCE(col2,'Null') not like '%del%'