MySQL & PHP - Not unique table/alias

Question

I get the following error listed below and was wondering how do I fix this problem.

Not unique table/alias: \'grades\'

Here is the code I think

Answer 1

You need to use an alias if you're using the same name twice:

SELECT FROM grades g1 ... 
JOIN grades g2 ON g1.id = g2.grade_id ...

Be sure that you intended to use the same name twice, and didn't mistakenly enter the same name twice.