SQL Max-Min Difference Query | Dataford Interview Questions

Write a query to find the difference between the maximum and minimum values in a dataset where the maximum element always appears at a higher index than the smaller element.

Use dataset_values and evaluate the condition independently for each dataset_id. Ignore NULL values and exclude datasets without at least one valid ordered pair.

Output

Return one row per qualifying dataset with dataset_id and max_min_difference.
Sort by dataset_id ascending.

Schema

dataset_catalog

Column	Type	Description
dataset_idPK	INT	Unique dataset identifier
dataset_name	VARCHAR(100)	Human-readable dataset name

dataset_values

Column	Type	Description
value_idPK	INT	Unique value row identifier
dataset_id	INT	Dataset containing the value
element_index	INT	Position of the value within its dataset
element_value	INT	Numeric value at the specified index

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