CREATE FUNCTION ZilelePrecedente(@Data datetime)
RETURNS TABLE AS RETURN
SELECT @Data-CASE (DATEPART(weekday,@Data)+@@DATEFIRST)%7
        WHEN 0 THEN null
        WHEN 1 THEN null
        WHEN 2 THEN 3
        WHEN 3 THEN 1
        WHEN 4 THEN 1
        WHEN 5 THEN 1
        WHEN 6 THEN 1
    END AS Data
UNION ALL
SELECT @Data-CASE (DATEPART(weekday,@Data)+@@DATEFIRST)%7
        WHEN 0 THEN null
        WHEN 1 THEN null
        WHEN 2 THEN 4
        WHEN 3 THEN 4
        WHEN 4 THEN 2
        WHEN 5 THEN 2
        WHEN 6 THEN 2
    END AS Data
GO
SELECT * FROM ZilelePrecedente('20080918')

Răzvan