Question

我的搜索页面上有6个下拉列表，2个文本框和一个asp.net web表单应用程序中的按钮。单击按钮后，我需要选择过滤数据到转发器组件。当用户使用SQL Select Command在所有下拉列表中选择一些值时，我可以这样做。

SELECT * FROM Profiles WHERE (Sport = @Sport, Region = @Region, Name LIKE @Name,...)

但是当用户离开一些下拉列表或文本框时，空SQL命令不会显示任何内容。有人可以帮助我，如何解决这个问题？

修改我修改了查询，但它仍无效。

SELECT Profiles.ProfileId,Profiles.ProPicUrl, Profiles.Name, Profiles.Specialization, UsersSports.Rating " + _
                             "FROM Profiles " + _
                                 "JOIN UsersSports ON Profiles.ProfileId = UsersSports.ProfileId " + _
                                "WHERE (UsersSports.SportId = CASE WHEN @SportId != '' THEN @Sport ELSE UsersSports.SportId END) AND (Region = CASE WHEN @Region != '' THEN @Region ELSE Region END) AND (Specialization = CASE WHEN @Specialization != '' THEN @Specialization ELSE Specialization END)" + _
                                        "AND (Sex = CASE WHEN @Sex != '' THEN @Sex ELSE Sex END) AND ((@AgeFrom IS NOT NULL AND @AgeTo IS NOT NULL AND Age BETWEEN @AgeFrom AND @AgeTo) OR (@AgeFrom IS NULL AND @AgeTo IS NULL AND Age)) " + _
                                        "AND ((@PractiseFrom IS NOT NULL AND @PractiseTo IS NOT NULL AND Practise BETWEEN @PractiseFrom AND @PractiseTo) OR (@PractiseFrom IS NULL AND @PractiseTo IS NULL AND Practise))" + _
                                        "AND ((@Name IS NOT NULL AND Name LIKE '%@Name%') OR (@Name IS NULL AND Name))  AND ((@City IS NOT NULL AND City LIKE '%@City%') OR (@City IS NULL AND City))" + _
                                "ORDER BY UsersSports.Rating ASC

Answer 1

应如下所示 - 只需确保未选择下拉列表时，参数设置为NULL：

SELECT * FROM Profiles 
WHERE (@Sport IS NULL OR Sport = @Sport)
    AND (@Region IS NULL OR Region = @Region)
    AND (@Name IS NULL OR Name LIKE @Name)

Answer 2

SELECT * FROM Profiles WHERE (Sport = ISNULL(@Sport, Sport), Region = ISNULL(@Region, Region), Name LIKE ISNULL(@Name, Name),...

如果“empty”不是NULL（但是说空字符串），那么你可以选择使用CASE，就像这样

SELECT * FROM Profiles WHERE (Sport = CASE WHEN @Sport != '' THEN @Sport ELSE Sport END, ...

Answer 3

尝试以下内容：

String query = "SELECT * FROM Profiles WHERE";

if(ddlSports.SelectedIndex>0)
  query +=" Sports='"+ddlSports.SelectedValue+"' &";

if(!String.IsNullOrEmpty(txtRegion.Text))
  query +=" Region='"+txtRegion.Text+"' &"
..
.. 
..
and so on

query = query.TrimEnd('&');

使用下拉列表过滤从数据库中选择

3 个答案: