Demonic Posted August 25, 2008 Share Posted August 25, 2008 Alright I understand how to use a basic "JOIN" clause, but whats up with all this: LEFT JOIN, RIGHT JOIN, INNER JOIN, OUTTER JOIN I'm at the basic join lol whats needed for the other stuff? While we're on the subject, groupby, I was reading on w3schools about groupby, whats another use for groupby besides averaging results, I only understand GroupBy to be used to average columns and what not. Quote Link to comment Share on other sites More sharing options...
fenway Posted August 25, 2008 Share Posted August 25, 2008 LEFT and RIGHT are OUTER joins. JOIN is an INNER join (it's implied). Usually, I would write INNER JOIN vs. LEFT JOIN to make the distinction. LEFT vs. INNER -- normally, with an INNER join, if there are non-matching rows based on the join condition, no rows will be returned. With a LEFT join, rows from the first table with non-matching rows will yield NULLed out column for the fields in the second table -- making it possible to find non-matches (like movie reviews without votes, etc.). RIGHT is the opposite, but the convention is to use LEFT JOIN. Quote Link to comment Share on other sites More sharing options...
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