OUTER are ignored.
FULL is not implemented in MySQL.
FROM a,b WHERE a.x=b.y) is frowned on; use
FROM a JOIN b ON a.x=b.y instead.
FROM a JOIN b ON a.x=b.y includes rows that match in both tables.
LEFT JOIN b ON a.x=b.y
includes all rows from
a, plus matching data from
NULLs if there is no matching row.