Considere duas tabelas X e Y, com as seguintes instância...

select *

from X FULL JOIN Y on X.a=Y.c

select *

from X LEFT JOIN Y on X.a=Y.c

select *

from Y RIGHT JOIN X on X.a=Y.c

select *

from X CROSS JOIN Y on X.a=Y.c

select *

from X INNER JOIN Y on X.a=Y.c