Is there a shorter version of this query?

[jakesee]

Hi,

I don't know what is LEFT JOIN at all, but i accidentally made this query work. Can someone tell me if there is a shorter version of this query?

SELECT j . * , k.report
FROM (
 SELECT x . * , y.category AS parent_category
 FROM AccountCategories x
 LEFT JOIN AccountCategories y ON x.parent_category_id = y.category_id
) j
LEFT JOIN AccountReports k ON j.report_id = k.report_id

If possible, would you show me what is the meaning of LEFT JOIN, RIGHT JOIN, INNER JOIN and OUTER JOIN? I've read alot of tutorials but I can only understand CROSS JOIN so far.