Unpivot A Table In SQL | Dataford Interview Questions

How would you unpivot a given table from columns to rows?

Use the security_monthly_returns table. Convert the four monthly return columns into one row per security, date, and month, excluding missing monthly returns.

Output

Return security_id, as_of_date, month, and return_value.
Include one row for each non-null monthly return.
Order by security_id, as_of_date, and month in calendar order.

Schema

security_monthly_returns

Column	Type	Description
security_id	VARCHAR(12)	Security identifier
as_of_date	DATE	Observation date
jan_return	NUMERIC(8,5)	January return
feb_return	NUMERIC(8,5)	February return
mar_return	NUMERIC(8,5)	March return
apr_return	NUMERIC(8,5)	April return

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