SQL优化where条款中的条件

Question

在asp中，我设置了几个下拉菜单，允许用户根据选择来筛选页面上显示的数据。

这些下拉列表是数据收集，一年组例如11年，主题例如英语，教学组和一个子组。

数据的采集，年和主题都必须选择，但教学组和子组可以保留不选（全选），单独选择中选出的。

我在哪里SQL存储过程的条款是因为在亚组的许多选项现在巨大。以下是几个选项，其中没有选择子组或者选择了女孩子组或者选择了男子子组。除此之外还有很多，但为了简洁起见，我限制了我发布的内容。

我的问题是我可以以任何方式优化此代码，还是我最简洁？如果你需要更多的例子，请让我知道，我会将它们添加到帖子中。

where 

--All 
(@TeachingGroup = 'Select All' AND ([StuYear] = @StuYear) AND ([DataCollection] = @DataCollection) AND ([Name] = @SubjectName) AND @Subgroup='Select All' 
OR 
@TeachingGroup <> 'Select All' AND ([StuYear] = @StuYear) AND ([DataCollection] = @DataCollection) AND ([Name] = @SubjectName) AND ([TeachingGroup] = @TeachingGroup) AND @Subgroup='Select All') 
or 
--Gender Girls 
(@TeachingGroup = 'Select All' AND ([StuYear] = @StuYear) AND ([DataCollection] = @DataCollection) AND ([Name] = @SubjectName) AND Gender = 
case when @Subgroup = 'GenF' then 'F' end) 
OR 
@TeachingGroup <> 'Select All' AND ([StuYear] = @StuYear) AND ([DataCollection] = @DataCollection) AND ([Name] = @SubjectName) AND ([TeachingGroup] = @TeachingGroup) AND Gender = case when @Subgroup = 'GenF' then 'F' end 
or 
--Gender boys 
(@TeachingGroup = 'Select All' AND ([StuYear] = @StuYear) AND ([DataCollection] = @DataCollection) AND ([Name] = @SubjectName) AND Gender = 
case when @Subgroup = 'GenM' then 'M' end) 
OR 
@TeachingGroup <> 'Select All' AND ([StuYear] = @StuYear) AND ([DataCollection] = @DataCollection) AND ([Name] = @SubjectName) AND ([TeachingGroup] = @TeachingGroup) AND Gender = case when @Subgroup = 'GenM' then 'M' end 

Answer 1

如果您有更多的条件，您可能需要研究动态SQL，您可以根据提供的内容构建不同的查询。

而且，这将是相当标准的做法，通过“空”是指“全选”

然而，这是你所拥有的一个简单的版本：

Where 
    [StuYear] = @StuYear And 
    [DataCollection] = @DataCollection And 
    [Name] = @SubjectName And (
     @TeachingGroup = 'Select All' Or 
     [TeachingGroup] = @TeachingGroup 
    ) And (
     @SubGroup = 'Select All' Or 
     Gender = Case 
       When @SubGroup = 'GenF' Then 'F' 
       When @SubGroup = 'GenM' Then 'M' 
      End 
    ) 

动态SQL例如

Declare 
    @params nvarchar(max) = ' 
@StuYear int, 
@DataCollection varchar(30), 
@SubjectName varchar(30), 
@TeachingGroup varchar(30), 
@SubGroup varchar(30)', --replace with your definitions 
    @sql nvarchar(max) = ' 
Select 
    xxx 
from 
    xxx 
Where 
    [StuYear] = @StuYear And 
    [DataCollection] = @DataCollection And 
    [Name] = @SubjectName' 

If @TeachingGroup != 'Select All' 
    Set @sql += ' And TeachingGroup = @TeachingGroup' 

If @SubGroup != 'Select All' 
    Set @sql += ' And Gender = Right(@SubGroup, 1)' 

Exec sp_executesql @sql, @params, 
    @StuYear, @DataCollection, @SubjectName, @TeachingGroup, @SubGroup 

Answer 2

我会使用动态SQL。这增加越来越Index Seek因为所有谓词使用AND连接的机会（也，执行计划将存储开始不像OPTION (RECOMPILE)相同@SqlStatement的第二次执行）：

DECLARE @StuYear INT, 
     @DataCollection VARCHAR(100), 
     @SubjectName NVARCHAR(50), 
     @TeachingGroup VARCHAR(100), 
     @Subgroup VARCHAR(3); 

SELECT @StuYear = 2013, 
     @DataCollection = 'Col1', 
     @SubjectName = N'Mark', 
     @TeachingGroup = 'Select All', 
     @Subgroup = 'GenM'; 

DECLARE @SqlStatement NVARCHAR(MAX), @Params NVARCHAR(MAX); 

SET @SqlStatement = N' 
SELECT ... 
FROM ... 
where 1=1 
AND  ([StuYear] = @StuYear) 
AND  ([DataCollection] = @DataCollection) 
AND  ([Name] = @SubjectName) ' + CHAR(13) 
+ CASE 
     WHEN @TeachingGroup <> 'Select All' THEN N'AND  ([TeachingGroup] = @TeachingGroup) ' + CHAR(13) 
     ELSE N'' 
    END 
+ CASE 
     WHEN @Subgroup = 'GenF' THEN N'AND  ([Gender] = ''F'') ' + CHAR(13) 
     WHEN @Subgroup = 'GenM' THEN N'AND  ([Gender] = ''M'') ' + CHAR(13) 
     ELSE N'' 
    END; 

-- PRINT @SqlStatement; 

SET @Params = N'@StuYear INT, @DataCollection VARCHAR(100), @SubjectName NVARCHAR(50)'; 

EXEC sp_executesql 
     @SqlStatement, 
     @Params, 
     @StuYear = @StuYear, 
     @DataCollection = @DataCollection, 
     @SubjectName = @SubjectName; 

注：你应该替换所有变量的数据类型，最大长度（以及必要时的归类），包括用作sp_executesql中参数的变量（请参阅SET = @Params = ...）。