Trying to make a conditional join

Can someone tell me why the following code wont work? I think it's pretty self explonatory so no need try explain what I want to do. (ask if need)

Code:

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SELECT * FROM messages AS msg
CASE msg.app_type
    WHEN 'study_abroad' THEN LEFT JOIN apps_study_abroad ON msg.application_id=apps_study_abroad.id
    WHEN 'study_in_china' THEN LEFT JOIN apps_study_in_china ON msg.application_id=apps_study_in_china.id
END CASE

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How about just joining both 3 tables and just put a where clause at the end?

yeah, that should work. thanks mate

no problem mate. =)