Join Where Rows Don't Exist or Where Criteria Matches...?

database-design, sql, sql-server, sql-server-2008

Solution

;WITH PromoCTE AS
(   SELECT  promo.*, CASE WHEN p.PromoCode IS NULL THEN 0 ELSE 1 END [HasPackage]
    FROM    Promo
            LEFT JOIN
            (   SELECT  DISTINCT PromoCode
                FROM    PromoPackage
            ) p
                ON promo.PromoCode = p.PromoCode
)
SELECT  [Order].OrderID, 
        CASE WHEN COUNT(CASE WHEN HasPackage = 1 THEN PromoPackage.PromoCode ELSE Promo.PromoCode END) >= 1 THEN 1 ELSE 0 END [IsPromoCodeValid]
FROM    [Order]
        LEFT JOIN PromoCTE promo
            ON Promo.PromoCode = [Order].OrderPromoCode
            AND [Order].OrderTimeStamp BETWEEN Promo.PromoStartTimestamp AND Promo.PromoEndTimestamp
        LEFT JOIN PromoPackage
            ON PromoPackage.PromoCode = OrderPromoCode
            AND PromoPackage.PackageID = [Order].PackageID
            AND [Order].OrderTimeStamp BETWEEN PromoPackage.PromoStartTimestamp AND PromoPackage.PromoEndTimestamp
GROUP BY [Order].OrderID;

NON CTE VERSION

SELECT  [Order].OrderID, 
        CASE WHEN COUNT(CASE WHEN HasPackage = 1 THEN PromoPackage.PromoCode ELSE Promo.PromoCode END) >= 1 THEN 1 ELSE 0 END [IsPromoCodeValid]
FROM    [Order]
        LEFT JOIN 
        (   SELECT  promo.*, CASE WHEN p.PromoCode IS NULL THEN 0 ELSE 1 END [HasPackage]
            FROM    Promo
                    LEFT JOIN
                    (   SELECT  DISTINCT PromoCode
                        FROM    PromoPackage
                    ) p
                        ON promo.PromoCode = p.PromoCode
        ) promo
            ON Promo.PromoCode = [Order].OrderPromoCode
            AND [Order].OrderTimeStamp BETWEEN Promo.PromoStartTimestamp AND Promo.PromoEndTimestamp
        LEFT JOIN PromoPackage
            ON PromoPackage.PromoCode = OrderPromoCode
            AND PromoPackage.PackageID = [Order].PackageID
            AND [Order].OrderTimeStamp BETWEEN PromoPackage.PromoStartTimestamp AND PromoPackage.PromoEndTimestamp
GROUP BY [Order].OrderID;

Problem

I'm trying to write a query to tell me which orders have valid promocodes. Promocodes are only valid between certain dates and optionally certain packages. I'm having trouble even explaining how this works (see psudo-ish code below) but basically if there are packages associated with a promocode then the order has to have one of those packages and be within a valid date range otherwise it just has to be in a valid date range. The whole "if PrmoPackage rows exist" thing is really throwing me off and I feel like I should be able to do this without a whole bunch of `Union`s. (I'm not even sure if that would make it easier at this point...) Anybody have any ideas for the query? ``` if `OrderPromoCode` = `PromoCode` then if `OrderTimestamp` is between `PromoStartTimestamp` and `PromoEndTimestamp` then if `PromoCode` has packages associated with it //yes then if `PackageID` is one of the specified packages //yes code is valid //no invalid //no code is valid ``` Order: ``` OrderID* | OrderTimestamp | PackageID | OrderPromoCode 1 | 1/2/11 | 1 | ABC 2 | 1/3/11 | 2 | ABC 3 | 3/2/11 | 2 | DEF 4 | 4/2/11 | 3 | GHI ``` Promo: ``` PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* ABC | 1/1/11 | 2/1/11 ABC | 3/1/11 | 4/1/11 DEF | 1/1/11 | 1/11/13 GHI | 1/1/11 | 1/11/13 ``` PromoPackage: ``` PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* | PackageID* ABC | 1/1/11 | 2/1/11 | 1 ABC | 1/1/11 | 2/1/11 | 3 GHI | 1/1/11 | 1/11/13 | 1 ``` Desired Result: ``` OrderID | IsPromoCodeValid 1 | 1 2 | 0 3 | 1 4 | 0 ```

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