Mysql SELECT CASE WHEN something then return field

Question

I have two field nnmu and nnmi ,

if nnmu is equal to 1, I need to return naziv_mesta from **mesto_istovara**, else if it's =0 I need to return naziv_mesta from mesto_utovara table 

and reverse,

if nnmi is equal to 1, then I need  to return naziv_mesta from **mesto_utovara,**  else if it's =0 need to return naziv_mesta from mesto_istovara. 

At first everything looks good, but somehow it mix up values, it work when nnmi and nnmu both are equal to 0, but when either value is 1 it returns nonsense. Any help?

select u.id_utovar,              u.datum_isporuke,              u.broj_otpremnice,              r.naziv_robe,                            CASE u.nnmu                WHEN u.nnmu ='0' THEN mu.naziv_mesta               WHEN u.nnmu ='1' THEN m.naziv_mesta              ELSE 'GRESKA'              END as mesto_utovara,              CASE u.nnmi               WHEN u.nnmi = '0' THEN m.naziv_mesta                WHEN u.nnmi = '1' THEN mu.naziv_mesta               ELSE 'GRESKA'              END as mesto_istovara,                                                              m.adresa,              m.kontakt_osoba,              m.br_telefona,              u.broj_paleta,              u.bruto,              k.username,              u.napomena,                                v.registracija,              p.naziv_prevoznika,              u.cena,              u.korisnik_logistika,              u.korisnik_analitika,              u.datum_unosa,              u.vreme_unosa,              u.zakljucan,              u.id_mesto_utovara,              u.id_mesto_istovara,              u.nnmu,              u.nnmi                    FROM utovar u ,mesto_utovara mu, mesto_istovara m, roba r, vozila v,prevoznik p, korisnik k       WHERE u.id_mesto_istovara=m.id_mesto_istovara        and k.id_korisnik = u.korisnik        and r.id_robe=u.id_robe         and u.id_mesto_utovara = mu.id_mesto_utovara         and v.id_vozilo = u.id_vozilo         and p.id_prevoznik = u.id_prevoznik        ORDER by u.id_utovar DESC 

Answer 1

You are mixing the 2 different CASE syntaxes inappropriately.

Use this style (Searched)

  CASE     WHEN u.nnmu ='0' THEN mu.naziv_mesta   WHEN u.nnmu ='1' THEN m.naziv_mesta  ELSE 'GRESKA'  END as mesto_utovara, 

Or this style (Simple)

  CASE u.nnmu    WHEN '0' THEN mu.naziv_mesta   WHEN '1' THEN m.naziv_mesta  ELSE 'GRESKA'  END as mesto_utovara, 

Not This (Simple but with boolean search predicates)

  CASE u.nnmu    WHEN u.nnmu ='0' THEN mu.naziv_mesta   WHEN u.nnmu ='1' THEN m.naziv_mesta  ELSE 'GRESKA'  END as mesto_utovara, 

In MySQL this will end up testing whether u.nnmu is equal to the value of the boolean expression u.nnmu ='0' itself. Regardless of whether u.nnmu is 1 or 0 the result of the case expression itself will be 1

For example if nmu = '0' then (nnmu ='0') evaluates as true (1) and (nnmu ='1') evaluates as false (0). Substituting these into the case expression gives

 SELECT CASE  '0'   WHEN 1 THEN '0'   WHEN 0 THEN '1'  ELSE 'GRESKA'  END as mesto_utovara 

if nmu = '1' then (nnmu ='0') evaluates as false (0) and (nnmu ='1') evaluates as true (1). Substituting these into the case expression gives

 SELECT CASE  '1'   WHEN 0 THEN '0'   WHEN 1 THEN '1'  ELSE 'GRESKA'  END as mesto_utovara