Question

我正在尝试在视图中编写子查询以作为列返回，但我不确定什么会给我最有效的调用。我有一个View A，它从不同的表中收集了一堆字段（一个表Listings与OpenHours有1对多的关系）然后我希望它来自另一个表的一个字段（OpenHours）只会是今天的开放时间字段。

OpenHours表格有ListingID，Day（0表示星期几），小时（开放时间的文字，例如＆＃34;上午8点 - 5:00 pm"）。这是我需要做的：

检查OpenTable是否有day = 7特定列表的记录，如果其为7（不是一周中的某一天），则返回＆＃34; 24小时开放＆＃34;。
如果不存在，则返回下一条记录，因为SQL Server datepart(dw..基于1，以下将使用select datepart(dw,getdate())-1来获取从星期日（星期日）开始的0天基础日0）
如果没有符合条件的记录，则不返回任何内容。

我希望得到一些帮助。我试图写这个，但无法走远。我不确定如何在视图中声明星期几的变量。

更新这是我的功能，任何人都看到任何明显的低效率？

ALTER FUNCTION [dbo].[GetTodaysOpenHours](@ListingID int) 
RETURNS VARCHAR(50)
AS
BEGIN
DECLARE @DayOfWeek int
--SQL Day of week starts on sunday but it is 1 based, listing open hours are 0 based
SET @DayOfWeek = DATEPART(DW, GETDATE()) - 1
DECLARE @OpenHours VARCHAR(50)
IF EXISTS(SELECT * FROM OpenHours WHERE Day = 7 AND ListingID = @ListingID) 
    SET @OpenHours = 'Open 24 Hours'
ELSE    
    SELECT @OpenHours  =  Hours FROM OpenHours WHERE ListingID = @ListingID AND Day = @DayOfWeek    

RETURN @OpenHours
END

更新后的视图

ALTER view [dbo].[vListings]
as
SELECT  l.ListingID, l.ExpiryDate, l.IsApproved, l.IsActive,      l.Position,MoneyField1, DateField1, 
    IntField1, IntField2, IntField3, IntField4, 
    BoolField1, BoolField2, BoolField3,  
    OptionField1, OptionField2, OptionField3, OptionField4, 
    IsTop, TopStartDate, TopExpireDate, Address, Address + ' ' + c.Name + ' ' + p.Name AS FullAddress, 
    o1.Description as Options1Description,
    o2.Description as Options2Description,
    o3.Description as Options3Description,
    o4.Description as Options4Description, 
    COALESCE(
              (SELECT TOP 1 ThumbnailPath
               FROM Attachments
               WHERE ListingID = l.listingID), '/content/images/noImageThumbnail2.jpg') AS MainThumbnail,
               COALESCE(
              (SELECT TOP 1 ThumbnailPath2
               FROM Attachments
               WHERE ListingID = l.listingID), '/content/images/noImageThumbnail.jpg') AS MainThumbnail2,
    l.UserID,
    c.SubDomainName as CitySubDomainName, l.Name,
    CASE 
        WHEN l.IsAutoGenerated = 1  THEN l.ImportedPhoneNumber
        ELSE  dbo.FormatPhoneNumber(u.PhoneNumber)
    END as PhoneNumber,
    CASE 
        WHEN l.IsAutoGenerated = 1  THEN l.ImportedContactInfo
        ELSE  u.FirstName + ' ' + u.LastName
    END as ContractInfo,
    p.Abbv as StateAbbv,
    cn.Code as CountryCode,
    l.Comments, l.UniqueID, l.Rating, l.Website, 
    (select    L.ListingID,
isnull(H1.Hours, H2.Hours) as Hours
from Listings L
    outer apply (
        select Hours FROM OpenHours H WHERE H.Day = 7 
        AND H.ListingID = L.ListingID
    ) H1
     outer apply (
        select Hours FROM OpenHours H WHERE Day = DATEPART(DW, GETDATE()) - 1
        AND H.ListingID = L.ListingID
    ) H2
        --dbo.GetTodaysOpenHours(l.ListingID) as TodaysOpenHours


FROM Listings l
    INNER JOIN Cities c ON c.CityID = l.CITYID
    INNER JOIN Provinces p ON p.ProvinceID = c.ProvinceID
    INNER JOIN Countries cn ON cn.CountryID = p.CountryID
    INNER JOIN AspNetUsers u ON u.Id = l.UserID
    LEFT OUTER JOIN Options1 o1 ON o1.OptionID = l.OptionField1
    LEFT OUTER JOIN Options2 o2 ON o2.OptionID = l.OptionField2
    LEFT OUTER JOIN Options3 o3 ON o3.OptionID = l.OptionField3
    LEFT OUTER JOIN Options4 o4 ON o4.OptionID = l.OptionField4

GO

我收到一条错误，指出＆＃34;关键字FROM附近的语法不正确（来自清单l）

我还将视图（添加了FROM）添加到了select语句中

我不喜欢使用它的功能，因为我必须在listingid和day上为我的openhours表添加一个索引，以便使它更快一点但是如果将sql添加到视图本身会更好，那将是很棒的

Answer 1

用户定义的功能通常不是性能最佳的解决方案。您可以尝试通过执行此类操作将该SQL添加到视图/查询中（抱歉，无法对此进行测试，希望没有语法错误）：

select
    L.ListingID,
    isnull(H1.Hours, H2.Hours) as Hours
from Listing L
    outer apply (
        select Hours OpenHours H WHERE H.Day = 7 
        AND H.ListingID = L.ListingID
    ) H1
     outer apply (
        select Hours OpenHours H WHERE Day = DATEPART(DW, GETDATE()) - 1
        AND H.ListingID = L.ListingID
    ) H2

T SQL子查询效率

1 个答案: