Best Way to make a "hashtag" system
Three tables will do the trick:
Contents, Hashtags, and ConTags. ConTags will be a junction table containing contents.id and hashtags.id. In this way, you can attribute multiple hashtags to each item in Contents.
SELECT * FROM Contents c, Hashtags h LEFT JOIN ConTags t ON c.Id = t.ConId AND h.Id = t.HashIdAlternatively, set Hashtags Name and ContentId as unique key and the junction table is no longer needed
Actually, one extra table is enough
"hashtags" (id(INT11), hashtag(VARCHAR(40))), content_id(int11))
Now you can simply add hastag's by name. To get all hashtags for a content, use
SELECT hashtag FROM hashtable WHERE content_id=$content_idTO add a remove a hashtag, delete it using its id or hashtag itself. To get content for specific hastags, just use
SELECT ct.* from hashtable ht, contenttable ct WHERE ht.hashtag=$hastag and ct.id=ht.content_idand so on