sql - MYSQL- Update Row Based on Fields From Another Row In Same Table -

i have "matches" table holds matches various games. looks (team1 , team2 correspond team ids)

team1|team2|tourney_identity|tourney_next|winner 5       6          1              3          6 7       8          2              3          7 0       0          3              5          0 

team 0 "tbd" , placeholder when teams arent decided yet.

i need query can run continuously grab winner match, update match has matching identity tourney_next

it needs able see if needs update team1 or team2

the final table should this:

team1|team2|tourney_identity|tourney_next|winner  5       6          1              3          6  7       8          2              3          7  6       7          3              5          0 

this current subquery have isnt working, place start

update matches m,(     select *, case when t1score > t2score team1 else team2 end winner   matches   isnull(round_id)=false , tourney_next<>0 , event_id=$event   order tourney_next) m2   set    m.team1= case when (m.team1=0 or isnull(m.team1)=true) , m.team2!=winner winner else m.team1 end ,   m.team2= case when (m.team1!=0 , isnull(m.team1)=false) , m.team1!=winner winner else m.team2 end   m.tourney_identity=m2.tourney_next , m.event_id=m2.event_id