Question

Right now the below query returns 1 row for each result…. I need to show a list of tags for each row and I’m debating whether to change this query so it INNER JOINS the tags and parsing out the data on the PHP end, or if I should just run a separate query for each return result…. what are your thoughts on this? Should I pull the extra data and parse it on the PHP end or run additional queries (maybe 25-30)?

            SELECT
                content.id,
                content_text.content
            FROM content
            INNER JOIN content_text ON (
                content_text.content_id = content.id AND
                content_text.language_id = 1
            )
            INNER JOIN tags_to_content ON (
                tags_to_content.tag_id IN (1)
            )

Answer 1

You could rely on a small command that is not used much in mysql : GROUP_CONCAT().

Official Doc for GROUP_CONCAT

Here is a small example (not based on your current question since I don’t know the specifics, its a example that could apply to a blog):

SELECT
  p.title as title,
  p.content as content,
  GROUP_CONCAT(c.name order by c.name SEPARATOR ', ') as categories
FROM
  post as p
INNER JOIN
  post_category as pc
ON
  p.id = pc.post_id
INNER JOIN
  category as c
ON
  pc.category_id = c.id
GROUP BY
  p.id

Which would return

+------------------+--------------------+------------------------------------+
| title            | content            | categories                         |
+------------------+--------------------+------------------------------------+
| Some title       | Some content       | category 1, category 2, category 3 |
| Some other title | Some other content | category 1, category 3, category 4 |
...
+------------------+--------------------+------------------------------------+