Getting most tagged posts

Question

So I want to find the most posted hashtag for my post system. So here's what my posts table looks like

+--------------+------------------+------+-----+---------+----------------+
| Field        | Type             | Null | Key | Default | Extra          |
+--------------+------------------+------+-----+---------+----------------+
| id           | int(11) unsigned | NO   | PRI | NULL    | auto_increment |
| post_user    | varchar(255)     | NO   |     |         |                |
| post_ip      | varchar(255)     | NO   |     |         |                |
| post_date    | varchar(255)     | NO   |     |         |                |
| post_content | varchar(40)      | NO   |     |         |                |
| post_likes   | varchar(255)     | YES  |     | NULL    |                |
| hashtag      | varchar(255)     | YES  |     | NULL    |                |
+--------------+------------------+------+-----+---------+----------------+

Now I want to query through and find the most used hashtag . So If I had two posts with the hashtag cats , it would return the number of cats, which would be 2 . Then I'd sort in descending order. So 2 for cats, and say 1 for dogs. So essentially the main question is how can I get the most "tagged", hashtag.

Answer 1

Your SQL would look something like:

SELECT count(hashtag) as c, hashtag FROM posts WHERE hashtag IS NOT NULL GROUP BY hashtag ORDER BY c DESC

This would return the list of hashtags, sorted by most used. The response will have two columns: c, which is the tag count and the tag itself.

If you just want the single most used tag:

SELECT count(hashtag) as c, hashtag FROM posts WHERE hashtag IS NOT NULL GROUP BY hashtag ORDER BY c DESC LIMIT 1

This table design limits you to one hashtag per post. If you wanted to allows posts to have multiple hashtags, you would need a few more tables. Hashtags and posts have a many-to-many relationship: A post can have many tags, and a tag can be used in many posts. To model this, you would need a table for hashtags, and a table that connects posts and tags. The hashtag table could have just an ID column and a column for the tag. The junction table would have a column of the post id and a column for the tag ID. To associate a tag with post, put a row in the junction table that references the tag and the post. You could then remove the hashtag column from the posts table.