Using an alias

Question

Hi,
we have a composite key on a few of our tables. I was wondering what would be the best approach to see if a record from the one table exists in the other, and I wanted to use an alias:
select col1||''|col2||''||col3||''||col4 as id
from table1
where id in (select col1||''|col2||''||col3||''||col4)
from table2
I realize the above is not correct, and I can use a join statement as: where table1.col1 = table2.col1
but I was wondering if we could use an alias, and how/if we could do that?
appreciate it
Message was edited by:
user577001

Answer 1

You can check the performance of a join vs;
SQL> create table table1 as (
   select 1 col1, 2 col2, 3 col3, 4 col4, 10 some_val from dual union all
   select 1 col1, 2 col2, 3 col3, 4 col4, 20 some_val from dual union all
   select 0,0,0,0,30 from dual)
Table created.
SQL> create table table2 as (
   select 1 col1, 2 col2, 3 col3, 4 col4 from dual)
Table created.
SQL> select some_val
from table1
where (col1, col2, col3, col4) in (
          select col1, col2, col3, col4
          from table2)
  SOME_VAL
        20
        10