How to convert multiple string values in a single row from nvarchar to int

Question

suppose I have a table like below.all these values are in nvarchar. How would I find the minimum year from START_DATE??
PRODUCT_CODE 
PRODUCT_DESC
START_DATE
P00002933
VITAMINE C
2005,2000,2011,2001,2002
P00003087
BIOFENAC
2011,2009,2006,2007,2004,2005
P00000155
AMOXYPEN
2006,2007,2008,2009,0000,2001
P00002325
SAHHA FARINE
2008,2003,2002,2001,2009
P00005666
AMOXYPEN
2007,2008,2006,2009,0000,2001

Answer 1

Create the split function:
CREATE FUNCTION Split (
@InputString VARCHAR(8000),
@Delimiter VARCHAR(50)
RETURNS @Items TABLE (
Item VARCHAR(8000)
AS
BEGIN
IF @Delimiter = ' '
BEGIN
SET @Delimiter = ','
SET @InputString = REPLACE(@InputString, ' ', @Delimiter)
END
IF (@Delimiter IS NULL OR @Delimiter = '')
SET @Delimiter = ','
--INSERT INTO @Items VALUES (@Delimiter) -- Diagnostic
--INSERT INTO @Items VALUES (@InputString) -- Diagnostic
DECLARE @Item VARCHAR(8000)
DECLARE @ItemList VARCHAR(8000)
DECLARE @DelimIndex INT
SET @ItemList = @InputString
SET @DelimIndex = CHARINDEX(@Delimiter, @ItemList, 0)
WHILE (@DelimIndex != 0)
BEGIN
SET @Item = SUBSTRING(@ItemList, 0, @DelimIndex)
INSERT INTO @Items VALUES (@Item)
-- Set @ItemList = @ItemList minus one less item
SET @ItemList = SUBSTRING(@ItemList, @DelimIndex+1, LEN(@ItemList)-@DelimIndex)
SET @DelimIndex = CHARINDEX(@Delimiter, @ItemList, 0)
END -- End WHILE
IF @Item IS NOT NULL -- At least one delimiter was encountered in @InputString
BEGIN
SET @Item = @ItemList
INSERT INTO @Items VALUES (@Item)
END
-- No delimiters were encountered in @InputString, so just return @InputString
ELSE INSERT INTO @Items VALUES (@InputString)
RETURN
END -- End Function
GO
Use the below script:
create table Table1 (Product_Code varchar(50),Product_Desc varchar(10),sStart_date varchar(MAX))
Insert into Table1 Values('P00002933','VITAMINE C','2005,2000,2011,2001,2002'),
('P00003087','BIOFENAC','2011,2009,2006,2007,2004,2005')
Select Product_Code,Product_Desc ,MIN(Item) Minstart_date
From Table1 A
Cross apply Split(A.sStart_date,',') B
Group by Product_Code,Product_Desc
Drop table Table1