Transforming Relational Algebra Expressions
Transformations involving multiple kinds of operators
Select can be pushed below a join
Example (Assignment 5, query 2):
select distinct m.message_date
from member u join routing r on u.member_id = r.from_member_id
join message m on r.message_id = m.message_id
where u.name = 'Zyrianyhippy'
order by m.message_date desc;
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