INNER
and OUTER
are ignored.
FULL
is not implemented in MySQL.
"commajoin" (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.
FROM a
LEFT JOIN b ON a.x=b.y
includes all rows from a
, plus matching data from b
, or NULLs
if there is no matching row.