mysql - Select a field from sql IF, otherwise select another -

i have 3 fields in table designated structure relations between ids. means, example, 1 of 3 fields first_id, other 1 second_id , third 1 the_third_one. each combination of the_third_one , first_id , second_id "unique".

what want pick first_id if other_id equal second_id, or pick second_id if other_id equal first_id.

so basically, table structure this

first_id second_id the_third_one

2323 242 idrelatedstring

239 231 anotherone

and on.

my other_id 2323. want retrieve second_id , the_third_one.

my other_id 231. want retrieve first_id , the_third_one.

how should proceed query database?

try case when then

example:

select   third_id,   case when other_id = second_id first_id         when other_id = first_id  second_id   end id my_table ....