Show data that is not found in another table

I'm working on a classes database with specific users. When a user checks off a class as complete, it is added to a "ClassUser" table with the specific classID as well as the userID that completed the class. Now what I want to do is show a list of classes that the user has NOT taken from the primary Classes table.

So far, I have this SQL statement.

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This gives me a list of all classes found in the Classes table that are NOT in the ClassUser table. This is almost what I want, but now I want to add another condition so it only returns classes that userID=20 has not taken.

As of now this SQL statement returns the classes that all of the users haven't taken but I want to only see the classes that a specific user hasn't taken.

I've tried AND WHERE user_id=20 ,but I get no results from that.

Does anyone have any ideas?

http://imgur.com/2EA1.jpg

That is a picture of my current tables.

Once again, my goal is to display the list of classes that a specific user has not taken, where the table "ClassUser" represents the classes that a specific user has taken.

Hi marcuswilderby,

Try this:

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Cheers,

P.S. ~ Are you in the same class with jimmycantler?