substring - MYSQL: multiple functions in query String -

the following query not working in mysql (a trigger)

set new.uniq = substr(md5(concat(new.lat, '-', new.lon)),0,5)

only if delete substr give me correct output

set new.uniq = md5(concat(new.lat, '-', new.lon))

the problem zero:

set new.uniq = substr(md5(concat(new.lat, '-', new.lon)),0,5)                                                          ^

for example:

select substr('whatever', 0, 5) --> returns empty string select substr('whatever', 1, 5) --> returns 'whate'

change 0 1 , should fine:

set new.uniq = substr(md5(concat(new.lat, '-', new.lon)),1,5)

Call