DB2では空文字はNULLちゃうの

create table xxx(aaa varchar(5))

insert into xxx(aaa) values(NULL)

insert into xxx(aaa) values('')

insert into xxx(aaa) values('hello')

select count(*) from xxx where aaa is null
→1

select count(*) from xxx where aaa = ''
→1

select count(*) from xxx where aaa is null or aaa = ''
→2

ほほう。こういうOracleとのビミョウな違いが憎らしいｗ