SQL查詢和asp.net

Question

你好朋友以下是我的查詢其中displaylist是對象如果stringBuilder有零長度有時，但在這種情況下，它給出錯誤附近FROM語法不正確，所以我如何避免這個問題我需要寫一個在其他如果形式來避免這個或請建議我做一個最好的解決方案，也從來看

string cmd = @"SELECT [tbl_course].course_name as Course_Name , [tbl_branch].branch_name as Branch_Name,"+displayList+@" FROM [tbl_students], [tbl_course], [tbl_branch] 
         WHERE [tbl_students].course_id= @courseId 
         AND [tbl_students].branch_id IN(" + branchId + @") 
         AND (@firstYrPercent is null OR[tbl_students].first_year_percent>=@firstYrPercent) 
         AND (@secondYrpercent is null OR[tbl_students].second_year_percent>=@secondYrPercent) 
         AND (@thirdYrPercent is null OR[tbl_students].third_year_percent>=@thirdYrPercent) 
         AND (@finalYearpercent is null OR[tbl_students].final_year_percent>=@finalYearpercent) 
         AND (@currentDegeePercentage is null OR[tbl_students].current_degree_percent>=@currentDegeePercentage) 
         AND (@passoutYear is null OR[tbl_students].passing_year>=@passoutYear) 
         AND (@currentBacklog is null OR[tbl_students].current_backlog<=@currentBacklog) 
         AND [tbl_students].gender=@sex 
         AND (@eGap is null OR [tbl_students].gapin_education<=@eGap) 
         AND (@highSchoolPercentge is null OR[tbl_students].highschool_percentage>=@highSchoolPercentge) 
         AND (@higherSchoolPercentage is null OR[tbl_students].ssc_percentage>=@higherSchoolPercentage) 
         AND (@grauationPercentage is null OR[tbl_students].graduation_percentage>=@grauationPercentage) 
         AND (@diplomaPercentage is null OR[tbl_students].diploma_percentage>=@diplomaPercentage) 
         AND (@noOfAtkt is null OR[tbl_students].number_of_ATKT<=@noOfAtkt) 
         AND (@validDate is null OR[tbl_students].DOB<=@validDate) 
         AND [tbl_students].branch_i 

d=[tbl_branch].branch_id AND [tbl_students].course_id=[tbl_course].course_id"; 

Answer 1

問題是你插入顯示列表的價值就在接近逗號效率和性能點不同的查詢。如果顯示列表是空的，那麼你的SQL語句如下所示：

...[tbl_branch].branch_name as Branch_Name, FROM [tbl_students]... 

因此，無論包括dispalyList（displayList = ", [tbl_branch].branch_foo"）逗號或使用條件語句，將其插入SQL時：

string cmd = @"SELECT [tbl_course].course_name as Course_Name , [tbl_branch].branch_name as Branch_Name" + String.IsNullOrEmpty(displayList) ? "" : ", " + displayList + @" FROM [tbl_students]...";