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Where the Funnel Leaks

hardSQLSubqueriesAggregation

The steepest fall in Kindled's funnel is the last one: the gap between putting something in a basket and paying for it. Before anyone argues about why, the growth lead wants the two headcounts sitting on a single line so the leak is visible at a glance — how many people reached a basket, and how many of them got as far as paying. Both figures count people, so a shopper who carted three times is one person.

events — one row per tracked action. user_id points at a row in users. event_type is one of signup, view_product, add_to_cart and purchase. event_date is the day the action happened. Nothing guarantees a person produces all four kinds, or any particular number of rows.

id user_id event_type event_date
1 1 signup 2023-05-01
2 1 view_product 2023-05-01
3 1 add_to_cart 2023-05-02
4 1 purchase 2023-05-03
5 2 signup 2023-05-02
6 2 view_product 2023-05-02
7 3 signup 2023-05-03
8 3 view_product 2023-05-03
9 3 add_to_cart 2023-05-04
10 4 signup 2023-05-04
11 4 view_product 2023-05-05
12 4 add_to_cart 2023-05-05
13 4 purchase 2023-05-06
14 5 signup 2023-05-05
15 6 signup 2023-05-06
16 6 view_product 2023-05-06
17 7 signup 2023-05-07
18 7 view_product 2023-05-07
19 7 add_to_cart 2023-05-08
20 7 purchase 2023-05-09
21 8 signup 2023-05-08

The table already exists in the database — there is nothing to create or load.

Task: Write a query that returns exactly one row with two columns, carted and purchased — how many separate people have at least one basket action, and how many have at least one purchase.

Example output — the shape, on invented figures. One row, two columns, side by side rather than stacked:

carted purchased
26 11

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