$re = '/((^|\s)(right|inner|left)\sjoin\s(.*?)on\s(.*?)(?=(inner|right|where)?))+/mi';
$str = 'SELECT a, b, c, de, efe
FROM aaa a, bbb b
inner join aaa aa ON aa = aaa
right join vvv aac On vvv.asdw = adadw AND ccc = aadw
left join aaaa aa On aaa = sss WHERE a = \'aa\'';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php