Подскажите пож-та какое решение этой ошибки?

SELECT        t_MaxValidFrom.MCode, t_MaxValidFrom.LatestPL_ValidFrom, t_MaxValidFrom.PL_TypeId, 
CByte(Nz(tbl_ref_PriceList_Body.UnitNetPrice, 0)) AS IsInLatestPL

FROM (tbl_ref_PriceList_Header INNER JOIN tbl_ref_PriceList_Body ON tbl_ref_PriceList_Header.PL_Id = tbl_ref_PriceList_Body.PL_Id) 
INNER JOIN 
(
SELECT  tbl_ref_PriceList_Body.MCode, tbl_ref_PriceList_Header.PL_TypeId, MAX(tbl_ref_PriceList_Header.PL_ValidFro) AS LatestPL_ValidFrom
FROM tbl_ref_PriceList_Body INNER JOIN
tbl_ref_PriceList_Header ON tbl_ref_PriceList_Body.PL_Id = tbl_ref_PriceList_Header.PL_Id
GROUP BY tbl_ref_PriceList_Body.MCode, tbl_ref_PriceList_Header.PL_TypeId 
) 
AS t_MaxValidFrom ON(tbl_ref_PriceList_Body.MCode = t_MaxValidFrom.MCode) AND (tbl_ref_PriceList_Header.PL_TypeId = t_MaxValidFrom.PL_TypeId) AND (tbl_ref_PriceList_Header.PL_ValidFrom = t_MaxValidFrom.LatestPL_ValidFrom)
ORDER BY t_MaxValidFrom.MCode, t_MaxValidFrom.PL_TypeId, t_MaxValidFrom.LatestPL_ValidFrom

http://www.sql.ru/forum/1099933/type-mismatch-in-join-expression-error-3615