Interview Query

New Notification

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Twitter wants to roll out more push notifications to users because they think users are missing out on good content. Twitter decides to do this in an A/B test. 

Let’s say that after we release more notifications, we suddenly see the total number of unsubscribes increase.

We’re given two tables, events where actions are login, nologin, and unsubscribe and another table called variants where user’s are bucketed into a control and a variant a/b test.

Given these tables, write a query to display a graph to understand how unsubscribes are affecting login rates over time.

Note: Let’s say that all users are automatically put into the A/B test.

Example:

Input:

event table

Column Type
user_id INTEGER
created_at DATETIME
action VARCHAR

Output:

variants table

Column Type
user_id INTEGER
experiment VARCHAR
variant VARCHAR
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MySQL 8.0.17
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