How to extract dates from a varchar string - sql-server-2005

Question

How to extract dates from a varchar string;
Format of data:
Rates from 16th April 2011 to 31st Aug 2011
I want output as '16/04/2011' and '31/08/2011'
Regards,
Nitin

Answer 1

To do not play with day end part like "d","st" etc, it is better to split your string into words and then analyse it. Double spaces being removed at the beginning.
DECLARE #s NVARCHAR(MAX)= 'Rates from 16th April 2011 to 2st Aug 2011'
SET #s = REPLACE(#s, ' ', ' ')
DECLARE #BegDay VARCHAR(2)= '' ,
#begMonth NVARCHAR(100) ,
#BegYear VARCHAR(4)
DECLARE #EndDay VARCHAR(2) ,
#EndMonth NVARCHAR(100) ,
#EndYear VARCHAR(4)
DECLARE #BegDate DATETIME ,
#EndDate DATETIME
DECLARE #Words TABLE
(
Word NVARCHAR(1000) ,
WordNr INT
) ;
WITH c ( Char, Pos, WordNr )
AS ( SELECT SUBSTRING(#s, 1, 1) CHAR ,
1 ,
CAST(0 AS BIGINT)
UNION ALL
SELECT SUBSTRING(#s, pos + 1, 1) CHAR ,
pos + 1 ,
CASE WHEN SUBSTRING(#s, pos + 1, 1) = SPACE(1)
THEN c.WordNr + 1
ELSE c.WordNr
END
FROM c
WHERE pos < LEN(#s)
)
INSERT INTO #Words
( Word ,
WordNr
)
SELECT RTRIM(LTRIM(SUBSTRING(#s, c.Pos,
ISNULL(c2.Pos, LEN(#s)) - c.Pos + 1))) ,
c.WordNr + 1
FROM ( SELECT *
FROM c
) c
LEFT OUTER JOIN C C2 ON c2.WordNr = c.WordNr + 1
AND c2.Char = ' '
WHERE c.char = ' '
OR c.Pos = 1 ;
WITH c ( Word, [CHAR], Pos )
AS ( SELECT T.Word ,
CAST(SUBSTRING(T.Word, 1, 1) AS NVARCHAR(100)) ,
1
FROM #Words T
WHERE WordNr = 3
UNION ALL
SELECT c.Word ,
CAST(SUBSTRING(c.Word, 1, pos + 1) AS NVARCHAR(100)) ,
pos + 1
FROM c
WHERE ISNUMERIC(SUBSTRING(C.Word, c.pos + 1, 1)) = 1
)
SELECT TOP 1
#BegDay = char
FROM c
ORDER BY pos DESC
SET #begMonth = ( SELECT T.Word
FROM #Words T
WHERE T.WordNr = 4
)
SET #BegYear = ( SELECT T.Word
FROM #Words T
WHERE T.WordNr = 5
)
SET #BegDate = #BegDay + '' + #begMonth + #Begyear ;
WITH c ( Word, [CHAR], Pos )
AS ( SELECT T.Word ,
CAST(SUBSTRING(T.Word, 1, 1) AS NVARCHAR(100)) ,
1
FROM #Words T
WHERE WordNr = 7
UNION ALL
SELECT c.Word ,
CAST(SUBSTRING(c.Word, 1, pos + 1) AS NVARCHAR(100)) ,
pos + 1
FROM c
WHERE ISNUMERIC(SUBSTRING(C.Word, c.pos + 1, 1)) = 1
)
SELECT TOP 1
#EndDay = char
FROM c
ORDER BY pos DESC
SET #EndMonth = ( SELECT T.Word
FROM #Words T
WHERE T.WordNr = 8
)
SET #EndYear = ( SELECT T.Word
FROM #Words T
WHERE T.WordNr = 9
)
SET #EndDate = #EndDay + '' + #EndMonth + #Endyear
SELECT #BegDate Begindate ,
#EndDate EndDate