比使用IF更适合这种情况吗？

Question

我正在写一个网站上使用的查询。当需要查询时，它直接被解析到服务器，结果全部由查询控制。该网站只是返回表格。我在网站上做的是客户端可以选择的复选框，并将这些复选框解析为查询@var = 1或@var = 0。正因为如此，现在我有这个代码来检查和添加或不取决于它是否被检查。我的问题是，有没有更好的办法去这比使用IF声明是这样，因为我有代码的几个部分，其中包括这样的：

SET @sql = 'select distinct ' 
If @mgchk = 1 
    SET @sql = @sql + 'p.MainGroup' 
If @sgchk = 1 and @sql = 'select distinct ' 
    SET @sql = @sql + 'p.SubGroup' 
If @sgchk = 1 and @sql not like '%SubGroup' 
    SET @sql = @sql + ',p.SubGroup' 
If @ssgchk = 1 and @sql = 'select distinct ' 
    SET @sql = @sql + 'p.SubSubGroup' 
If @ssgchk = 1 and @sql not like '%SubSubGroup' 
    SET @sql = @sql + ',p.SubSubGroup' 
If @Seasonchk = 1 and @sql = 'select distinct ' 
    SET @sql = @sql + 'p.Season' 
If @Seasonchk = 1 and @sql not like '%Season' 
    SET @sql = @sql + ',p.Season' 
If @vendorchk = 1 and @sql = 'select distinct ' 
    SET @sql = @sql + 'p.VendorID' 
If @vendorchk = 1 and @sql not like '%VendorID' 
    SET @sql = @sql + ',p.VendorID' 

SET @sql = 
    @sql + 
    ' into 
     ##aa 
    from 
     RPProducts p, 
     RPIv i, 
     RPTrsd d, 
     RPTrs s 
    WHERE 
    s.StoreID = d.StoreID and 
     s.ReceiptNO = d.ReceiptNO and 
     i.UPC = d.UPC and 
     i.StoreID = d.StoreID and 
     i.IVProduct = p.Productid and 
     s.TRSdate >= '''+ convert(varchar(10), @trsfrom, 101) +''' and 
     s.TRSdate <= '''+ convert(varchar(10), @trsto, 101) +'''' 
execute sp_executesql @sql 

@mgchk/@sgchk/@ssgchk/@seasonchk/@vendorchk是复选框变量

要回答@Aaron，

全局临时因为动态查询。整个查询得到处理并在数据被拖动时立即丢弃。没有冲突会发生在那里。

我的日期变量是datetime，它在动态SQL中给我一个错误。

是的，回想一下同样的事情来检查，这是整个问题的原因，如果有更好的使用比IF检查。

，我发现使用别名连接更容易...

Answer 1

-- rather than convert to a dangerously formatted string, 
-- here is a much better way to strip time from a datetime 
-- (if you need to!) 

SET @trsfrom = DATEADD(DAY, DATEDIFF(DAY, 0, @trsfrom), 0); 
SET @trsto = DATEADD(DAY, DATEDIFF(DAY, 0, @trsto), 0); 

DECLARE @sql NVARCHAR(MAX) = N'SELECT DISTINCT '; 

-- here's an easier way to strip the first comma: 

SET @sql += SUBSTRING(
    CASE WHEN @mgchk  = 1 THEN ',p.MainGroup' ELSE '' END 
    + CASE WHEN @sgchk  = 1 THEN ',p.SubGroup' ELSE '' END 
    + CASE WHEN @ssgchk = 1 THEN ',p.SubSubGroup' ELSE '' END 
    + CASE WHEN @Seasonchk = 1 THEN ',p.Season'  ELSE '' END 
    + CASE WHEN @vendorchk = 1 THEN ',p.VendorID' ELSE '' END, 2, 2000); 

SET @sql += ' INTO ##aa 
    FROM 
     dbo.RPProducts AS p -- use schema prefix! 
    INNER JOIN dbo.RPIv AS i -- use PROPER JOINS! 
     ON i.IVProduct = p.Productid 
    INNER JOIN dbo.RPTrsd AS d 
     ON i.UPC = d.UPC 
     AND i.StoreID = d.StoreID 
    INNER JOIN dbo.RPTrs AS s 
     ON s.StoreID = d.StoreID 
     AND s.ReceiptNO = d.ReceiptNO 
    WHERE s.TRSdate >= @trsfrom -- use strongly typed parameters! 
    AND s.TRSdate <= @trsto;'; 

EXEC sp_executesql @sql, 
    N'@trsfrom DATETIME, @trsto DATETIME', 
    @trsfrom, @trsto; 
----^^^^^^^^^^^^^^^^ here is how the query gets the @trsfrom & @trsto values 

我仍然认为你一个##全局临时表的使用是相当危险的。如果两个人同时运行这些代码，他们将会遇到严重的问题。