一种字段串的拆分

CREATE FUNCTION fn_getstring
(
@key VARCHAR(MAX) ,
@string VARCHAR(MAX) ,
@star INT ,
@step INT
)
RETURNS VARCHAR(MAX)
BEGIN
DECLARE @result VARCHAR(MAX)
SET @result = ''

SELECT @result = @result + SUBSTRING(words, n,
CHARINDEX(',', words + ',',
n) - n) + ','
FROM ( SELECT @string words
) array
JOIN dbo.Nums ON n <= LEN(words)
AND SUBSTRING(@key + words, n, 1) = @key
WHERE ( n - LEN(REPLACE(LEFT(words, n), @key, '')) + 1 ) BETWEEN @star
AND
@end

RETURN SUBSTRING (@result,1, LEN(@result)-1)
END