这查询有什么问题吗？请在语法上纠正我，这是错误的，请在此方面纠正我，如何将其连接起来

string cmd = "SELECT * 
                FROM [tbl_students] 
               WHERE course_id=@courseId 
                 AND branch_id IN ("+branchId+") 
                 AND (@passoutYear is null or passout_year>=@passoutYear) 
                 AND (@currentBacklog is null or current_backlog<=@currentBacklog)
                 AND gender=@sex 
                 AND (@eGap is null or gapin_education<=@egap)
                 AND (@firstYrPercent is null or first_yea_percent>=@firstYrPercent
                 AND (@secondYrpercent is null or second_year_percent>=@secondYrPercent)
                 AND (@thirdYrPercent is null or third_year_percent>=@thirdYrPercent)
                 AND (@finalYrpercent is null or final_year_percent>=@finalYrpercent)
                 AND (@currentDegreePercentage is null current_degree_percent>=@currentDegreePercentage)
                 AND (@highSchoolPercentage is null high_school_percentage>=@highSchoolPercentage)
                 AND (@higherSchoolPercentage is null higher_school_percentage>=@higherSchoolPercentage)
                 AND (@graduationPercent is null graduation_percent>=@graduationPercentage)
                 AND (@diplomaPercentage is null diploma_percentage>=@diplomaPercenage)
                 AND (@noOfAtkt is null or no_of_atkt<=@noOfAtkt)
                 AND (@date is null or date_of_birth>=@date)";