SQL Server CASE即使存在值也返回NULL

Question

Below is my sample Query. When I run the query the PreviousTotalQuantity returns null even there are data with in the date range.

SELECT
    p.ActualId,
    p.Name,
    p.QTYONHAND AS OnHand,
    p.PRICE AS DistCost,
    SUM(soi.Quantity) AS PresentTotal,
    SUM(CASE
        WHEN soi.MASSCHDSHIPDATE > '2014-3-1' AND
            soi.MASSCHDSHIPDATE < '2014-6-1' THEN soi.Quantity
        ELSE NULL
    END) AS PreviousTotalQuantity
FROM 
    sysdba.PRODUCT p
    LEFT OUTER JOIN sysdba.SALESORDERITEMS soi
        ON p.PRODUCTID = soi.PRODUCTID
WHERE 
    soi.MASSCHDSHIPDATE > '2015-3-1' AND 
    soi.MASSCHDSHIPDATE < '2015-6-1'
GROUP BY p.PRODUCTID, p.ACTUALID, p.NAME, p.QTYONHAND, p.PRICE

I need also to pull the data from the previous year with the given date.

Answer 1

Because your years are not in sync in select (2014) and where (2015) part

Edit

SELECT
    p.ActualId,
    p.Name,
    p.QTYONHAND AS OnHand,
    p.PRICE AS DistCost,
    SUM(soi.Quantity) AS PresentTotal,
    ISNULL(prev.TotalQty, 0) AS PreviousTotalQuantity
FROM 
    sysdba.PRODUCT p
    LEFT OUTER JOIN sysdba.SALESORDERITEMS soi
        ON p.PRODUCTID = soi.PRODUCTID
    OUTER APPLY
    (
        SELECT SUM(Quantity) AS TotalQty 
        FROM sysdba.SALESORDERITEMS 
        WHERE PRODUCTID = p.PRODUCTID 
            AND MASSCHDSHIPDATE > '2014-03-01' AND MASSCHDSHIPDATE < '2014-06-01'
    ) AS prev
WHERE 
    soi.MASSCHDSHIPDATE > '2015-03-01' AND 
    soi.MASSCHDSHIPDATE < '2015-06-01'
GROUP BY p.PRODUCTID, p.ACTUALID, p.NAME, p.QTYONHAND, p.PRICE, prev.TotalQty

Answer 2

Don't compare date manually.

Use between clause either

Declare @PRODUCT table
(
Name varchar(50),
Date datetime,
Quantity int
)

INSERT INTO @PRODUCT VALUES ('Nikunj','2014-3-1',20)
INSERT INTO @PRODUCT VALUES ('Nikunj','2014-6-1',40)
INSERT INTO @PRODUCT VALUES ('Nikunj','2014-9-1',60)
INSERT INTO @PRODUCT VALUES ('JayDeep','2014-3-1',10)
INSERT INTO @PRODUCT VALUES ('JayDeep','2014-9-1',20)

select Name, sum(Quantity),SUM(Case when Date between '2014-3-1' and '2014-6-1' then Quantity else NULL end) TotalQuantity from @PRODUCT 
where Date between '2014-3-1' and '2014-6-1' group by Name 

Try this accordingly and do check year in the where condition code.

Answer 3

The issue here is that you restrict rows in WHERE statement with year 2015 and because of it there are no rows in result set in year 2014. So you get NULL because of CASE works AFTER WHERE statement.

If you need select current 2015 year and count this field for 2014 you can use this query. I doesn't know if PRODUCTID is unique in sysdba.PRODUCT so I use subquery with DISTINCT. If these fields are unique in PRODUCTS just use FROM PRODUCTS P without DISTINCT subquery:

SELECT
    p.ActualId,
    p.Name,
    p.QTYONHAND AS OnHand,
    p.PRICE AS DistCost,
    soi2015.SUM_Quantity AS PresentTotal,
    soi2014.SUM_Quantity AS PreviousTotalQuantity
FROM 
    (SELECT  DISTINCT 
             p.ActualId,
             p.Name,
             p.QTYONHAND AS OnHand,
             p.PRICE AS DistCost,        
             FROM sysdba.PRODUCT 
    ) p 
    LEFT OUTER JOIN 
      (SELECT PRODUCTID,SUM(soi.Quantity)  SUM_Quantity
        FROM  sysdba.SALESORDERITEMS
        WHERE (MASSCHDSHIPDATE > '2015-03-01') 
               AND (MASSCHDSHIPDATE < '2015-06-1')
        GROUP BY PRODUCTID
      ) soi2015 ON (p.PRODUCTID = soi2015.PRODUCTID) 
    LEFT OUTER JOIN 
      (SELECT PRODUCTID,SUM(soi.Quantity)  SUM_Quantity
        FROM  sysdba.SALESORDERITEMS
        WHERE (MASSCHDSHIPDATE > '2014-03-01') 
               AND (MASSCHDSHIPDATE < '2014-06-1')
        GROUP BY PRODUCTID
      ) soi2014 ON (p.PRODUCTID = soi2014.PRODUCTID)