articles_categories1:
  article_id: 1
  category_id: 1

articles_categories2:
  article_id: 1
  category_id: 2

articles_categories3:
  article_id: 1
  category_id: 3

articles_categories4:
  article_id: 2 
  category_id: 3

articles_categories5:
  article_id: 3
  category_id: 3
  
articles_categories6:
  article_id: 4
  category_id: 3

articles_categories7:
  article_id: 1
  category_id: 5

articles_categories8:
  article_id: 18
  category_id: 6
