if object_id('[Table1]') is not null drop table [Table1]
go
create table [Table1] (postId int,sup_id int,realName nvarchar(4),postType int)
insert into [Table1]
select 1,12,'Tr',1 union all
select 2,13,'jk',1 union all
select 3,14,'pl',1

if object_id('[Table2]') is not null drop table [Table2]
go
create table [Table2] (postId int,sup_id int,realName nvarchar(4),postType int)
insert into [Table2]
select 1,12,'Tr',2 union all
select 2,13,'gk',2 union all
select 3,14,'hj',2

select * from [Table1]
select * from [Table2]

select postid,sup_id,realname,MAX(posttype)
from (
select postid,sup_id,realname,posttype from Table1 
union 
select postid,sup_id,realname,posttype from Table2 ) T
group by postid,sup_id,realname

/*
1    12    Tr    2
2    13    gk    2
2    13    jk    1
3    14    hj    2
3    14    pl    1*/