Interview Query

Comments Histogram

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Write a SQL query to create a histogram of the number of comments per user in the month of January 2020.

Note: Assume bin buckets class intervals of one.

Note: Comments by users that were not created in January 2020 should be counted in a “0” bucket

Example:

Input:

users table

Columns Type
id INTEGER
name VARCHAR
created_at DATETIME
neighborhood_id INTEGER
mail VARCHAR

comments table

Columns Type
user_id INTEGER
body VARCHAR
created_at DATETIME

Output:

Column Type
comment_count INTEGER
frequency INTEGER
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MySQL 8.0.17
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