--Found at: http://www.algonet.se/~sommar/arrays-in-sql.html
CREATE FUNCTION iter_charlist_to_table
(@list ntext,
@delimiter nchar(1) = N',')
RETURNS @tbl TABLE (listpos int IDENTITY(1, 1) NOT NULL,
str varchar(4000) COLLATE Chinese_PRC_CI_AI,
nstr nvarchar(2000)) AS

BEGIN
DECLARE @pos int,
@textpos int,
@chunklen smallint,
@tmpstr nvarchar(4000),
@leftover nvarchar(4000),
@tmpval nvarchar(4000)

SET @textpos = 1
SET @leftover = ''
WHILE @textpos <= datalength(@list) / 2
BEGIN
SET @chunklen = 4000 - datalength(@leftover) / 2
SET @tmpstr = @leftover + substring(@list, @textpos, @chunklen)
SET @textpos = @textpos + @chunklen

SET @pos = charindex(@delimiter, @tmpstr)

WHILE @pos > 0
BEGIN
SET @tmpval = ltrim(rtrim(left(@tmpstr, @pos - 1)))
INSERT @tbl (str, nstr) VALUES(@tmpval, @tmpval)
SET @tmpstr = substring(@tmpstr, @pos + 1, len(@tmpstr))
SET @pos = charindex(@delimiter, @tmpstr)
END

SET @leftover = @tmpstr
END

INSERT @tbl(str, nstr) VALUES (ltrim(rtrim(@leftover)), ltrim(rtrim(@leftover)))
RETURN
END


declare @vchr varchar(100)
set @vchr = 'aa, bb'
select * from table1 where field in ( iter_charlist_to_table(@vchr) )