Which SQL statement requires an active running warehouse?

• A. SELECT MIN(ID) FROM t1
• B. SELECT MAX(ID) FROM t1
• C. SELECT AVG(ID) FROM t1
• D. SELECT COUNT(*) FROM t1

Answer: (C)

The key idea is that some aggregate calculations can be answered from metadata stored with micro-partitions, without scanning all the data. Snowflake keeps statistics like per-partition min, max, and row_count. You can often combine those to get MIN or MAX across the whole table and sum the per-partition row_counts for COUNT(*) without touching the actual rows. But AVG needs the total sum of all values and the total number of rows, which cannot be derived from metadata alone. To compute that accurately, the engine must read and process the data, so an active running warehouse is required for an AVG query.