Knowledge Articles Without Reactions

SQL practice question · Easy · Joins · Facebook

knowledge_pages lists every page (page_id, page_name) and page_reactions has one row per like (user_id, page_id). Some reaction rows may have a NULL page_id or point to a page id that is not in knowledge_pages. Return the page_id of every page in knowledge_pages that has never received a like. Output column: page_id. Order by page_id ascending.

Table: knowledge_pages

Schema of knowledge_pages
Column	Type
page_id	INTEGER
page_name	TEXT

Schema of knowledge_pages

Column

Type

page_id

INTEGER

page_name

TEXT

Sample rows of knowledge_pages
page_id	page_name
10	Technology
20	Education
30	Finance
40	Sports

Sample rows of knowledge_pages

page_id

page_name

Technology

Education

Finance

Sports

Table: page_reactions

Schema of page_reactions
Column	Type
user_id	INTEGER
page_id	INTEGER

Schema of page_reactions

Column

Type

user_id

INTEGER

page_id

INTEGER

Sample rows of page_reactions
user_id	page_id
101	10
102	10
103	30

Sample rows of page_reactions

user_id

page_id

101

102

103

Expected output on the sample data
page_id
20
40

Expected output on the sample data

page_id

Solve it in the live editor on this page — run on sample data, then submit against hidden tests.

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