小编Ale*_*hev的帖子

create database test

create table test.A (id UInt8, data String) engine MergeTree() order by (id)

create table test.B (id UInt8, data String) engine MergeTree() order by (id)

insert into test.A values (0,'a'),(1,'b'),(2,'c')

insert into test.B values (1,'x'),(2,'y'),(3,'z')

select *, isNull(a.id), isNull(b.id) from test.A a full join test.B b on a.id = b.id

如何判断0是0还是0是Null？