65. Signup Funnel Conversion
A funnel measures how many users progress through ordered stages. Chained CTEs make each stage a named, reusable step: count distinct users who visited, then those who added to cart, then those who purchased, and finally compute conversion rates between stages.
Three event tables share a user_id. A user is counted at a stage if they have at least one row in that stage's table.
Task: produce a one-row funnel summary: distinct visitors, cart users, purchasers, and the two conversion rates as percentages rounded to 1 decimal — visit→cart and cart→purchase.
Return columns visitors, carts, purchases, visit_to_cart_pct, cart_to_purchase_pct (one row).
This is the result for the example data above. On Submit your query is graded against this example plus 4 hidden edge cases — 5test cases in all. A sloppy query that only fits the example won't pass.