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Chapter 9: Data Integration (Join (outer (right outer join (adds any rows…
Chapter 9: Data Integration
Join
combines two datasets with a shared identity value
ex: a customer identifier
inner
each row in the left table is combined horizontally with any row in the right table that has the same identity value
when dealing with carefully curated databases
outer
right outer join
adds any rows from the right table that donot have corresponding rows in the left table
produces the same result as an inner join
full outer join
produces the same result as an inner join + a left outer join + a right outer join
left outer join
produces the same result as an inner join but also adds any rows from the left table that do not have corresponding rows in the right table
use if engaged in a project with the goal being to collect as much customer data as possible
Union
based on the assumption that there are multiple columns in common between A and C
combines A and C to create a new table
datasets that contain unique sets of cases sharing the same or very similar columns