Multiple select queries using while loop in a single table? Is it Possible?

问题

I have 2 tables. Table A has Date, ISBN (for Book), Demand(demand for that date). Table B has Date, ISBN (for Book), and SalesRank.

The sample data is as follows: The DailyBookFile has 150k records for each date, from year 2010 (i.e. 150k * 365 days * 8 years) rows. Same goes with SalesRank Table having about 500k records for each date

DailyBookFile       
Date        Isbn13         CurrentModifiedDemandTotal
20180122    9780955153075   13
20180122    9780805863567   9
20180122    9781138779396   1
20180122    9780029001516   9
20180122    9780470614150   42

SalesRank       
importdate  ISBN13          SalesRank
20180122    9780029001516   69499
20180122    9780470614150   52879
20180122    9780805863567   832429
20180122    9780955153075   44528
20180122    9781138779396   926435

Required Output     
Date        Avg_Rank    Book_Group
20180122    385154  Elite
20180121    351545  Elite
20180120    201545  Elite

I want to get the Top 200 CurrentModifiedDemand for each day, and take the average Rank.

I am unable to work out a solution as I am new to SQL.

I started with getting the Top 200 CurrentModifiedDemand for yesterday and get the Avg Rank over last year.

SELECT DBF.Filedate AS [Date],
       AVG(AMA.SalesRank) AS Avg_Rank,
       'Elite' AS Book_Group 
FROM [ODS].[wholesale].[DailyBookFile] AS DBF
INNER JOIN [ODS].[MarketplaceMonitor].[SalesRank] AS AMA ON (DBF.Isbn13 = AMA.ISBN13
                                                        AND DBF.FileDate = AMA.importdate)
WHERE DBF.Isbn13 IN (SELECT TOP 200 Isbn13
                     FROM [ODS].[wholesale].[DailyBookFile]
                     WHERE FileDate = 20180122
                       AND CAST(CurrentModifiedDemandTotal AS int) > 200)
  AND DBF.Filedate > 20170101
GROUP BY DBF.Filedate;

But the result is not what I want. So, now I want the ISBN for the Top 200 CurrentModifiedDemand for each day and their avg rank. I tried with this.

DECLARE @i int;
SET @i = 20180122;
WHILE (SELECT DISTINCT(DBF.Filedate)
       FROM [ODS].[wholesale].[DailyBookFile] AS DBF
       WHERE DBF.Filedate = @i) IS NOT NULL
BEGIN

    SELECT DBF.Filedate AS [Date],
           AVG(AMA.SalesRank) AS Avg_Rank,
           'Elite' AS Book_Group 
    FROM [ODS].[wholesale].[DailyBookFile] AS DBF
    INNER JOIN [ODS].[MarketplaceMonitor].[SalesRank] as AMA ON DBF.Isbn13 = AMA.ISBN13
                                                            AND DBF.FileDate = AMA.importdate
    WHERE DBF.Isbn13 in (SELECT TOP 200 Isbn13
                         FROM [ODS].[wholesale].[DailyBookFile]
                         WHERE FileDate = @i
                           AND CAST (CurrentModifiedDemandTotal AS int) > 500)
      AND DBF.Filedate = @i
    GROUP BY DBF.Filedate;

    SET @i = @i+1;

END

In this I am getting one select query result in each window. Is there any way to have the result in a single table?

P.S. The list of top 200 books every day will change according to the CurrentModifiedDemand. I want to take their avg. sales rank for that day.

回答1:

Instead of immediately selecting in each iteration of the loop, you can insert rows to temp table (or table-type variable) and select everything after the loop finishes:

IF OBJECT_ID('tempdb..#books') IS NOT NULL
BEGIN
    DROP TABLE #books
END

CREATE TABLE #books (
    [Date] INT,
    [Avg_Rank] FLOAT,
    [Book_Group] VARCHAR(512)
);

DECLARE @i int;
SET @i = 20180122;

BEGIN TRY
WHILE (SELECT DISTINCT(DBF.Filedate)
    FROM [ODS].[wholesale].[DailyBookFile] AS DBF
    WHERE DBF.Filedate = @i) IS NOT NULL
BEGIN

    INSERT INTO #books (
        [Date],
        [Avg_Rank],
        [Book_Group]
    )
    SELECT DBF.Filedate AS [Date],
        AVG(AMA.SalesRank) AS Avg_Rank,
        'Elite' AS Book_Group 
    FROM [ODS].[wholesale].[DailyBookFile] AS DBF
    INNER JOIN [ODS].[MarketplaceMonitor].[SalesRank] as AMA ON DBF.Isbn13 = AMA.ISBN13
                                                            AND DBF.FileDate = AMA.importdate
    WHERE DBF.Isbn13 in (SELECT TOP 200 Isbn13
                        FROM [ODS].[wholesale].[DailyBookFile]
                        WHERE FileDate = @i
                        AND CAST (CurrentModifiedDemandTotal AS int) > 500)
    AND DBF.Filedate = @i
    GROUP BY DBF.Filedate;

    SET @i = @i+1;

END
END TRY
BEGIN CATCH
    IF OBJECT_ID('tempdb..#books') IS NOT NULL
    BEGIN
        DROP TABLE #books
    END
END CATCH

SELECT *
FROM #books

DROP TABLE #books

Using table-type variable would yield simpler code, but when storing large amounts of data table-type variables start losing in performance against temp tables. I'm not sure how many rows is a cut-off, but in my experience I've seen significant performance gains from changing table-type var to temp table at 10000+ row counts. For small row counts an opposite might apply.

回答2:

This avoids a costly WHILE loop, and I believe achieves your goal:

CREATE TABLE #DailyBookFile ([Date] date,
                            Isbn13 bigint,
                            CurrentModifiedDemandTotal tinyint);

INSERT INTO #DailyBookFile
VALUES ('20180122',9780955153075,13),
       ('20180122',9780805863567,9 ),
       ('20180122',9781138779396,1 ),
       ('20180122',9780029001516,9 ),
       ('20180122',9780470614150,42);

CREATE TABLE #SalesRank (importdate date,
                        ISBN13 bigint,
                        #SalesRank int);
INSERT INTO #SalesRank
VALUES ('20180122',9780029001516,69499 ),
       ('20180122',9780470614150,52879 ),
       ('20180122',9780805863567,832429),
       ('20180122',9780955153075,44528 ),
       ('20180122',9781138779396,926435);
GO
WITH Ranks AS(
    SELECT SR.*,
           RANK() OVER (PARTITION By SR.importdate ORDER BY SR.#SalesRank) AS Ranking
    FROM #SalesRank SR
         JOIN #DailyBookFile DBF ON SR.ISBN13 = DBF.Isbn13
                               AND SR.importdate = DBF.[Date])
SELECT importdate AS [Date],
       AVG(#SalesRank) AS Avg_rank,
       'Elite' AS Book_Group
FROM Ranks
WHERE Ranking <= 200
GROUP BY importdate;

GO
DROP TABLE #DailyBookFile;
DROP TABLE #SalesRank;

来源：https://stackoverflow.com/questions/48406026/multiple-select-queries-using-while-loop-in-a-single-table-is-it-possible

标签

sql-server

while-loop

with-statement