No credit card required
An inner join may drop some of the rows from the beginning tables. An outer join puts back some of those rows. There are three types of outer joins, each type adding back a different set of the dropped rows.
Introduction to Outer Joins
Outer joins are derived from inner joins
The three types of outer joins
The left outer join
The right outer join
The full outer join
An introduction to the union
An example of a union of two tables with matching columns
Applications of Outer Joins
Counting to zero, part 4
Combining an outer join with a selection of the data
A full outer join in sorted order
Finding the defects in a pattern
Comparing tables using two ...