Linking on names rather than ids

[ZooeyMiller]

in the seconds exercise you have to link the tables together like this:

SELECT mentors.name, count (post_num) FROM mentors
INNER JOIN posts
ON mentors.name = posts.mentor_name
INNER JOIN likes
ON posts.num = likes.post_num
GROUP BY mentors.name;

We are joining on names, and then on post_num.
Yesterday in our research we were led to believe that we should INNER JOIN on the IDs, not the names as those things can be variable, and joining on ID is then a consistent way for our databases to work.

I just wanted to raise an issue because I found it a bit confusing to join in a way I had been led to believe was bad practice.
(I may even have a wrong solution! Sorry if I'm wrong, just confused).

[ZooeyMiller]

Someone else just casted and showed this solution:

SELECT posts.mentor_name, COUNT(likes.post_num) 
FROM likes INNER JOIN posts
ON likes.post_num = posts.num
GROUP BY posts.mentor_name

Which shows you don't need to link on name, but you do still link on "num" rather than "id" which I still find a wee bit confusing.

[shiryz]

@ZooeyMiller , you're right about it being good practice to put an id in the table as a primary key, but you can still join by any column you'd like and it doesn't have to be the id.

[shiryz]

Closing, this is now outdated