DECLARE @Y nvarchar(50)=N'2008,2010,2013';
SELECT SUM(CASE Y WHEN YEAR(CURRENT_TIMESTAMP) THEN DATEPART(DAYOFYEAR,CURRENT_TIMESTAMP) ELSE 365+ISDATE(Y+N'0229') END) [CountOfDays]
FROM
(
SELECT SUBSTRING(@Y,V.number,
(
SELECT MIN(VV.number)
FROM master.dbo.spt_values VV
WHERE VV.type='P' AND VV.number BETWEEN V.number AND LEN(@Y)+1
AND CHARINDEX(SUBSTRING(@Y+N',',VV.number,1),N',')>0
)-V.number
)
FROM master.dbo.spt_values V
WHERE V.type='P' AND V.number BETWEEN 1 AND LEN(@Y)+1
AND CHARINDEX(SUBSTRING(N','+@Y,V.number,1),N',')>0
)T(Y);
Функция, которая делит строку на слова