Question

I have the following query. I need Description to be set to the value of the long statement in the middle – the part beginning with CONVERT and ending with [Description]. The query I have now runs but the value of Description in the result is always NULL. Any ideas?

select s.SectionId, 
    s.Academic_Year [AcademicYear],
    s.Academic_Term [AcademicTerm],
    s.Academic_Session [AcademicSession],
    s.Event_Id [EventId],
    s.Event_Sub_Type [EventSubType],
    s.Section [Section],
    s.Event_Long_Name [EventLongName],
    e.Description [EventDescription],
    CONVERT(varchar(MAX), S.DESCRIPTION) 
        + '<br /><br /><a href="http://www.bkstr.com/webapp/wcs/stores/servlet/booklookServlet?bookstore_id-1=044&term_id-1=' 
        +   CASE S.ACADEMIC_TERM 
            WHEN 'SPRING' THEN 'SPRING' 
            WHEN 'SUMMER' THEN 'SUM' 
            WHEN 'FALL' THEN 'FALL' 
            WHEN 'J TERM' THEN 'J TERM'
            ELSE 'ADV'
            END 
            + S.ACADEMIC_YEAR + '/' + 
            CASE S.ACADEMIC_SESSION
            WHEN '01' THEN '1' 
            WHEN '02' THEN '2' 
            WHEN '03' THEN '3' 
            END 
            + '&div-1=HILB&dept-1=' + SUBSTRING(S.EVENT_ID, 1, CHARINDEX(' ', S.EVENT_ID) - 1) + '&course-1=' + SUBSTRING(S.EVENT_ID, CHARINDEX(' ', S.EVENT_ID) + 1, 
            LEN(S.EVENT_ID)) + '&section-1=' + CONVERT(varchar(2), S.SECTION) + '" target=' + '"_blank">View Book Information</a>' [Description],
    cest.Medium_Desc [SubTypeDescription],
    s.Credits [Credits],
    cge.Medium_Desc [GeneralEd],
    s.Start_Date [StartDate],
    s.End_Date [EndDate],
    s.Max_Participant [MaximumParticipants],
    s.Adds [AddCount],
    s.Wait_List [WaitlistCount],
    s.Sec_Enroll_Status [EnrollmentStatus],
    o.Org_Name_1 [CampusName],
    cp.Medium_Desc [ProgramDescription],
    cc.Medium_Desc [CollegeDescription],
    cd.Medium_Desc [DepartmentDescription],
    ccm.Medium_Desc [CurriculumDescription],
    ccl.Medium_Desc [ClassLevelDescription],
    nt.Nontrad_Med_Name [NonTraditionalDescription],
    cpn.Medium_Desc [PopulationDescription],
    case s.Other_Org when 'N' then 0 else s.Other_Org_Part end as [CampusOtherLimit],
    case s.Other_Program when 'N' then 0 else s.Other_Program_Part end as [ProgramOtherLimit],
    case s.Other_College when 'N' then 0 else s.Other_College_Part end as [CollegeOtherLimit],
    case s.Other_Department when 'N' then 0 else s.Other_Dept_Part end as [DepartmentOtherLimit],
    case s.Other_Curriculum when 'N' then 0 else s.Other_Curric_Part end as [CurriculumOtherLimit],
    case s.Other_Class_Level when 'N' then 0 else s.Other_CLevel_Part end as [ClassLevelOtherLimit],
    case s.Other_NonTrad when 'N' then 0 else s.Other_NonTrad_Part end as [NonTraditionalOtherLimit],
    case s.Other_Population when 'N' then 0 else s.Other_Pop_Part end as [PopulationOtherLimit],
    s.Other_Org_Add as [CampusOtherRegistered],
    s.Other_Program_Add as [ProgramOtherRegistered],
    s.Other_College_Add as [CollegeOtherRegistered],
    s.Other_Dept_Add as [DepartmentOtherRegistered],
    s.Other_Curr_Add as [CurriculumOtherRegistered],
    s.Other_CLevel_Add as [ClassLevelOtherRegistered],
    s.Other_Nontrad_Add as [NonTraditionalOtherRegistered],
    s.Other_Pop_Add as [PopulationOtherRegistered],
    case s.Registration_Type when 'TRAD' then 0 else 1 end as [IsConEd],
    cat.Medium_Desc [TermDescription],
    cas.Medium_Desc [SessionDescription],
    s.Credit_Type [DefaultCreditType],
    cct.Medium_Desc [CreditTypeDescription]
    from sections s
    left join code_eventsubtype cest on cest.code_value_key = s.event_sub_type
    left join code_generaled cge on cge.code_value_key = s.general_ed
    left join event e on e.event_id = s.event_id
    left join organization o on o.org_code_id = s.org_code_id
    left join code_program cp on cp.code_value_key = s.program
    left join code_college cc on cc.code_value_key = s.college
    left join code_department cd on cd.code_value_key = s.department
    left join code_curriculum ccm on ccm.code_value_key = s.curriculum
    left join code_classlevel ccl on ccl.code_value_key = s.class_level
    left join nontraditional nt on nt.nontrad_program = s.nontrad_program
    left join code_population cpn on cpn.code_value_key = s.population
    left join code_acaterm cat on cat.code_value_key = s.academic_term
    left join code_acasession cas on cas.code_value_key = s.academic_session
    left join code_acacredittype cct on cct.code_value_key = s.credit_type

Answer 1

One of your inputs must be NULL.

You can probably solve this by identifying which it is and using COALESCE or ISNULL:

COALESCE(x, '')
ISNULL(x, '')

COALESCE is the standard ANSI way, ISNULL gives slightly better performance (although the difference is probably insignificant in most cases).