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$sql=mysql_query("SELECT * FROM post"); while($row=mysql_fetch_array($sql)) { $article_id=$row['article_id']; $all_tags=$row['all_tags']; $all_tags= explode(",",$all_tags); foreach($all_tags as $tag) { $sql2=mysql_query("SELECT * FROM tags WHERE tag_name = '$tag'"); while($row=mysql_fetch_array($sql2)) { $tag_id=$row['tag_id']; echo $tag_id . "<br>"; $q = "INSERT INTO post_tag (id_post, id_tag) VALUE ('$article_id', '$tag_id')"; $r = mysql_query($q); } } } I tried something like this, but it doesn't write all post_tag table

Hi all, I am trying to normalize my database I had table POST where the all tags have been saved (comma separated): POST: article_id all_tags 1 x1, x2, x3 2 x2, x3, x4 now I create new table TAGS and insert all tags from POST table in single column TAGS: tag_id tag_name 1 x1 2 x2 3 x3 I made POST_TAG (as map table) table but i have no idea how to populate it, how the query should look like, how to? POST_TAG: id_post id_tag 1 1 1 2 2 1 thank you