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