Question

I have a mysql db with an article (article_id, keyword) db table where keywords is a comma-separated list. I have created two new empty tables:

keywords (keyword_id, keyword) where each row has only one keyword.

article_key (article_id, keyword_id) where each row has only one keyword.

Thus I want to have a many-to-many relationship from articles to keywords. I wanted to create a short script to extract the id and keywords from the original article table, split the keywords and populate the two new tables appropriately. I assumed this would be easy, but has proved a little more tricky than I thought.

Any help would be much appreciated.

Answer 1

You could do something similar to this:

//Get articles with keywords:
$result = mysql_query("SELECT article_id, keyword FROM article");

//Cycle through all articles
while ($article = mysql_fetch_assoc($result)) {
     $article_id = $article['article_id'];
     $keywords = $article['keyword'];
     //Explode keywords on seperator (; in this case)
     $keyword_array = explode(";", $keywords);

     //For each keyword get the corresponding ID
     for ($i = 0; $i < count($keyword_array); i++) {
          $result2 = mysql_query("SELECT keyword_id FROM keywords WHERE keyword = '" . $keyword_array[$i] . "'");
          //Get keyword_id
          $row = mysql_fetch_assoc($result2);
          $keyword_id = $row['keyword_id'];

          //Insert new key
          mysql_query("INSERT INTO article_key VALUES (" . $article_id . ", " . $keyword_id . ")");
     }
}

In this script (not tested) I assumed you already have your keywords table filled with the keywords, and that your article table contains a comma seperated list of KEYWORDS and NOT id’s.