SQLite 简化了左外连接的并集

Question

I inherited some monster SQL queries and I would like to simplify/ shorten them as much as possible.

One of them is:

SELECT 
              * 
            FROM 
              (
                SELECT 
                  $columnsFromBothTables
                FROM 
                  table_abc
                  left outer join table_xyz using profile_id 
                union 
                select 
                  $columnsFromBothTables
                from 
                  table_xyz 
                  left outer join table_abc using profile_id
              ) 

It looks weirdly redundant.
Is there a way to simplify it to sth like?

SELECT * FROM (
    SELECT $columns FROM table_abc MAGIC_OPERATION table_xyz
)

Isn't it a FULL OUTER JOIN?

Updates : My understanding is that both tables have M-1 relationship to "profile" table.

They do not have direct relationship to each other

Answer 1

This is similar to but not exactly a full outer join . I would recommend this approach for the full outer join :

select $columns
from abc left join
     xyz
     on . . .
union all
select $columns
from xyz left join
     abc
     on . . .
where abc.? is null;  -- some column to validate that there is no match

Note: This does not remove duplicates -- which your code does. That is why this version should perform better. But it might not do exactly what you want.