Dynamic regular expressions in MySQL based on the contents of a table - mysql

Question

Is it possible to do this in MySQL?
select * from keyword
where keyword NOT REGEX concat('\b', concat_ws('\b|\b', (select distinct(keyword) from negative_keyword)), '\b')
limit 3;
It currently gives this error:
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'REGEX concat_ws('|', (select distinct(keyword) from negative_keyword)) limit 3' at line 1
The concat_ws by itself gives this error:
ERROR 1242 (21000): Subquery returns more than 1 row
I have to match whole words, not just substrings or exact matches. For example, negative keyword 'cat' should match 'black cat', but not 'catatonic'.

Answer 1

SELECT *
FROM x
WHERE NOT EXISTS
( SELECT *
FROM negative_keywords nk
WHERE nk.keyword = x.keyword
);

Answer 2

In the mean time, I had to filter them in code (PHP).
# filter negative keywords
$negatives = NegativeKeyword::find()->select('keyword')->distinct('keyword')->column();
$negatives = array_map(function($v) { return '/\b'.preg_quote($v).'\b/';}, $negatives); # escape regular expression, search whole words only
$kw = array_filter($kw, function($v) use ($negatives) {
foreach ($negatives as $n) {
if (preg_match($n, $v['keyword'])) { // strpos($v['keyword'], $n) !== false)
// echo "filtering $v[keyword]\n";
return false; // match found, filter word, break early
}
}
return true; // good to keep
});