Complex Data Integration and Joins Questions
Handling intricate join scenarios: multi-condition joins, conditional joins with complex logic, joining on date ranges or overlapping time periods, complex left joins with multiple filtering conditions, self-joins for hierarchical or relationship data, handling non-standard relationships between tables. Understanding implications of different join types on row counts, NULL values, and duplicate handling. Designing queries that correctly integrate data from multiple sources while maintaining data integrity and avoiding duplicate counting or missing data.
MediumTechnical
0 practiced
Write SQL to perform a left join with multiple complex filtering conditions: Orders joined to CouponRedemptions only when coupon_code matches, redemption_timestamp between order_ts - 1 day and order_ts + 7 days, and coupon was active at redemption. Ensure that orders with no redemptions remain in the result set with NULLs for coupon fields.
MediumTechnical
0 practiced
Provide SQL to compute an adjusted conversion rate where conversions are stored across two tables: ConversionsA(user_id, conv_ts) and ConversionsB(user_id, conv_ts). Some conversions appear in both tables (duplicates). Join both sources to Users and calculate unique conversions per user per month. Explain how you prevent double counting across the two sources.
HardTechnical
0 practiced
As a senior BI analyst, describe how you would architect a robust join-based reconciliation process across nightly ETL jobs to ensure that dimension key mismatches (foreign keys violating referential integrity) are detected, reported, and remediated before dashboards refresh. Include SQL checks and operational steps.
HardTechnical
0 practiced
Construct a query to join a sales fact to a promotional calendar where promotions have overlapping date ranges and priority levels. For a given sale date, attach the highest-priority active promotion. Tables: Sales(sale_id, sale_date) and Promotions(promo_id, start_date, end_date, priority INT). Use SQL to resolve overlaps deterministically.
EasyTechnical
0 practiced
You have an employee hierarchy table Employees(emp_id INT, manager_id INT, name TEXT). As a BI analyst, write a query to list each employee with their top-level manager (the manager with manager_id IS NULL) using a self-join or an alternative approach. Explain when you would use recursive CTEs vs iterative joins and implications for deep hierarchies.
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