mysql - Find the subtype by having the supertype Primary Key

Question

I have a Supertype/Subtype relationship for Products, Frames and Liquids, and now I want determine what subtype it is by having the supertype product_id. I'm using:

SELECT p.*
     , a.*
     , l.* 
  FROM products p
  LEFT 
  JOIN frames a 
    ON p.product_id = a.frame_id
  LEFT 
  JOIN liquids l 
    ON p.product_id = l.liquid_id
 WHERE p.product_id = 3

The product_id cannot be shared between the subtypes, so only one join gets data. That means I get a lot of fields that have nothing to do with the product that was found, and I dislike that a lot, to the point of being sure that there "must be another, better way".

Thank you.

question from:https://stackoverflow.com/questions/66069036/find-the-subtype-by-having-the-supertype-primary-key

Answer 1

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