Question

I have two mysql tables. One is a bad words list, the other is the table to compare against the bad words list. Essentially I want to filter out and return a list of rows with domains that do not have ANY occurrence of a word in the bad words table. A few sample tables:

bad words list

+----------+------------------+
| id       | words            |
+----------+------------------+
| 1        | porn             |
| 2        | sex              |
+----------+------------------+

table of domains to compare

+----------+------------------+
| id       | domain           |
+----------+------------------+
| 56       | google.com       |
| 57       | sex.com          |
+----------+------------------+

I want to return results such as

+----------+------------------+
| id       | domain           |
+----------+------------------+
| 56       | google.com       |
+----------+------------------+

A thing to note is that these tables have nothing in common, so I’m not even sure this is the best method. I was using a comparison function in PHP but that seemed to be way too slow over hundreds of thousands of rows to search.

Answer 1

It is possible to get from mysql. like this:

SELECT
    d.*
FROM 
    domains d 
LEFT JOIN
    words w ON(d.domain LIKE CONCAT('%',w.word,'%') ) 
GROUP BY
    d.domain
HAVING
    COUNT(w.id) < 1

but it is not optimal and will get slower and slower with more records in both tables.