Page 3 - Multiple Tables Without Relationship

Inner join vs outer join:

Inner join will remove rows from the first table if there is not a corresponding row in the 2nd table. Outer join will keep the rows, and use all NULL values to fill in the gaps in the 2nd table.

In general outer joins are more likely to grow a result set and inner joins are more likely to shrink one (though that will depend on the data and the query). For this reason, it is usually better when building complex queries to try to do your inner joins before your outer joins, because then you will keep your result set smaller for longer and thus the later joins can run faster.