小编Aza*_*h91的帖子

在下面的sql语句中,我收到以下错误

无法在GROUP BY子句列表中使用的表达式中使用聚合或子查询.

我怎么能绕过这个？

SELECT
    T.Post,
    COUNT(*) AS ClientCount,
    Client = CASE COUNT(*) WHEN '1' THEN T.Client ELSE '[Clients]' END
FROM
    MyTable T
GROUP BY
    T.Post,
    CASE COUNT(*) WHEN '1' THEN T.Client ELSE '[Clients]' END

我在Visual Studio中有一个ASP.Net网站解决方案,当Server.MapPath(@"\");我尝试收到以下错误时.我知道之前已经问过这个问题,但我还没有找到适合我的解决方案.任何想法都会很棒.

Failed to map the path '/'.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: Failed to map the path '/'.

Source Error: 


Line 10:     protected void Page_Load(object sender, EventArgs e)
Line 11:     {
Line 12:       string directory = Server.MapPath(@"\");
Line 13:       Response.Write(directory);
Line 14:     }

Source File: c:\Users\Josh\Documents\Visual Studio 2010\WebSites\MMCR\About.aspx.cs …

SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["cnnFinalProject"].ToString());
SqlCommand cmd = new SqlCommand(@"SELECT c.partID, p.name, p.categoryID, p.price, p.image, p.subCategoryID, 
                                        (CASE WHEN categoryID = 1 THEN 'Y' ELSE 'N' END) AS casesYN,
                                        (CASE WHEN categoryID = 3 THEN 'Y' ELSE 'N' END) AS OSYN,
                                        (CASE WHEN categoryID = 7 THEN 'Y' ELSE 'N' END) AS HDDYN,
                                        (CASE WHEN subCategoryID = 1 THEN 'Y' ELSE 'N' END) AS powerYN,
                                        (CASE WHEN subCategoryID = 2 THEN 'Y' ELSE 'N' END) AS processorYN,
                                        (CASE WHEN subCategoryID = …