database - a question on many-many relationships -

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i have following tables

  1. items
  2. similars
  3. items_similars = pivot table

items->similars has many-many relationship

the items_similars has following field

  1. item_id
  2. similar_id

if using innodb engine, need create relation between items.id , items_similars.id? or between similars.id , items_similars.id? or both?

are there advantages in doing or in not doing so?

many-to-many relationships, afaik, can implemented via transition tables (pivot tables) in rdbms. "items_similar" table should have @ least "items_id" , "similar_id" foreign keys "items" , "similars" tables' primary keys.


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