Constructing KPIs – 12-Month Retention Rate Let’s calculate a key performance indicator (KPI), which is a measurable value used to track progress toward a specific business goal. Definitions: A user’s start date is defined as the start date of their first policy with us. A user is considered retained if they have at least one valid policy exactly 12 months after their start date. A valid policy is one that has not ended or been canceled by that point. Task: Calculate the 12-month retention rate. Hint: First, identify each user’s earliest start_date. Then, check whether the user had a valid policy active exactly one year later. A valid policy must have: A start_date on or before the 12-month mark, and A policy_end_date or cancellation_date after the 12-month mark. You may need to use IFNULL() to handle policies without a cancellation date. Question: What percentage of users in the dataset were still active customers one year after their first policy began? Answer in decimals — for example, if your answer is 15%, write 0.15.数值题