Question

I have a table with that looks like

    Date    |  BookID   |  Rating  |  Review
2012-10-12  |    2      |    3     |    3
2012-10-13  |    2      |    7     |    9
2012-10-16  |    3      |    4     |    2

Each day, a book can receive a number of rating and review
I am trying to write a query that given two dates, it displays the rating and review for each book, for EACH day in between the two given dates. Even when that day has no rating or no review I still want to display the date and the BookID
For example, in the table above, I want the query to return something like

 Date       |  BookID   |  Rating  |  Review
2012-10-12  |    2      |    3     |    3
2012-10-13  |    2      |    7     |    9
2012-10-14  |    2      |   null   |   null
2012-10-15  |    2      |   null   |   null
2012-10-16  |    3      |    4     |    2

How can I do this please?

Answer 1

--set up test data

DECLARE @Reviews TABLE([Date] date, BookId int, Rating int, Review int)

INSERT INTO @Reviews VALUES
('2012-10-12', 2, 3, 3),
('2012-10-13', 2, 7, 9),
('2012-10-16', 3, 4, 2)

--setup query parameters
DECLARE @StartDate date, 
        @EndDate date
SELECT  @StartDate = '2012-10-12', 
        @EndDate = '2012-10-16'

--run query

;WITH IntervalSet AS
(
    SELECT @StartDate AS [Date]
    UNION ALL
    SELECT DATEADD(DAY,1,[Date]) AS [Date]
    FROM   IntervalSet 
    WHERE  DATEADD(DAY,1,[Date])<=@EndDate
) 
SELECT  I.[Date], B.BookId, R.Rating, R.Review 
FROM    
(
        SELECT  BookId, Min([Date]) as EarliestDate
        FROM    @Reviews
        GROUP BY BookId
) B
JOIN    IntervalSet I
        ON  I.[Date] >= b.EarliestDate
LEFT
JOIN    @Reviews R
        ON  R.[Date] = I.[Date]
        AND R.BookId = B.BookId
ORDER BY I.[Date], B.BookId
OPTION(MAXRECURSION 0)

This gives the results:

Date       BookId      Rating      Review
---------- ----------- ----------- -----------
2012-10-12 2           3           3
2012-10-13 2           7           9
2012-10-14 2           NULL        NULL
2012-10-15 2           NULL        NULL
2012-10-16 2           NULL        NULL
2012-10-16 3           4           2

That’s one extra row than the results you posted, but I believe is correct – it doesn’t return any rows for a bookid before the first review which looks like what you were after