Hard SQL With Window Functions | Dataford Interview Questions

Sum(case when attribute is true) Unions Hard SQL using window functions Python leetcode Easy

Use the provided entity and event tables. Combine the two event sources, remove exact duplicate records, and analyze events from January through March 2025.

Output

One row per entity and calendar month with events
Return entity_id, entity_name, month_start, event count, true-attribute count, prior-month true count, cumulative true count, and rank by monthly true count
Sort by entity_id, then month_start

Schema

entities

Column	Type	Description
entity_idPK	INT	Unique entity identifier
entity_name	VARCHAR(100)	Entity display name

current_entity_events

Column	Type	Description
event_idPK	INT	Unique event identifier within the source
entity_id	INT	Referenced entity
event_ts	TIMESTAMP	Event timestamp
attribute_is_true	BOOLEAN	Whether the event attribute is explicitly true

archived_entity_events

Column	Type	Description
event_idPK	INT	Unique event identifier within the source
entity_id	INT	Referenced entity
event_ts	TIMESTAMP	Event timestamp
attribute_is_true	BOOLEAN	Whether the event attribute is explicitly true

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