Notification Type Conversion

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We’re given two tables, a table of notification deliveries and a table of users with created and purchase conversion dates. If the user hasn’t purchased then the conversion_date column is NULL.

Write a query to get the conversion rate for each notification.

A user may convert only once.

Example:

notification_deliveries table

Column	Type
`notification`	VARCHAR
`user_id`	INTEGER
`created_at`	DATETIME

users table

Column	Type
`id`	INTEGER
`created_at`	DATETIME
`conversion_date`	DATETIME

Output:

Column	Type
`notification`	VARCHAR
`conversion_rate`	FLOAT

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MySQL 8.0.17

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