Easy Rookie SpeedRun joins inner-join fundamentals

SQL: Counting INNER JOIN Rows

+100 XP · 6 min · attempt 1

Problem

Given these two tables:

    users(id)        -> 1, 2, 3, 4
    orders(user_id)  -> 1, 1, 2, 2, 2, 5

How many rows does the following query return?

    SELECT u.id, o.user_id
    FROM users u
    INNER JOIN orders o ON o.user_id = u.id;

Enter a single integer.

Starter

-- Inner join keeps only rows whose join key exists on BOTH sides.
-- Each match emits one output row per (left, right) pair.

Your answer

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