Question

I’ve been scratching my head at this problem all day and I simple just can’t work it out. This is the first time I’ve attempted to try and use SQL Joining, while we do kinda get taught the basics I’m more into pushing a little more into the advanced stuff.

Basically I’m making my own forum, and I have two tables. f_topics (The threads) and f_groups (The forums, or categories). There is a relationship between topicBase in f_topics and groupID in f_groups, this shows which group each topic belongs to. Each topic has a unique ID called topicID and same for the groups, called groupID.

Basically, I’m trying to get all these columns into a single SELECT statement – The title of the topic, the date the topic was posted, the ID of the group the topic belongs in, and the name of that group. This is what I was trying to use, but the group always comes back as 1, even if the topic is in groupID 2:

$query=mysqli_query($link, "

SELECT `topicName`, `topicDate`, `groupName`, `groupID`
FROM `f_topics`
NATURAL JOIN `f_groups`
WHERE `f_topics`.`topicID`='$tid';


") or die("Failed to get topic detail E: ".mysqli_error());
var_dump(mysqli_fetch_assoc($query));

Sorry if this doesn’t make much sense, and if my entire logic is completely wrong, if so could you suggest an alternate method?

Thanks for reading!

Answer 1

To join tables, you need to map the foreign keys. Assuming your groups table has an groupID field, this is how you’d join them:

SELECT `topicName`, `topicDate`, `groupName`, `groupID`
FROM `f_topics`
LEFT JOIN `f_groups`
ON `f_topics`.`groupID` = `f_groups`.`groupID`
WHERE`f_topics`.`topicID`='$tid';