php - update user score from other tables -

i have few tables each have own scores each user. create trigger add scores each user , put them in field called score in users table.

tables (they have same fields few different ones) :  table 1 : {id, user_id, score} table 2 : {id, user_id, score} table 3 : {id, user_id, score}  users : {id, name, overall_score}  

// overall _score has value , want add score fields other tables one.

to achieve lets first write select query , sum of scores per user 3 given tables , how done

select u.*, y.total users u left join (   select user_id,sum(score) total from(     select user_id, score table_1     union     select user_id, score table_2     union     select user_id, score table_3   )x group x.user_id )y on y.user_id = u.id 

here demo http://www.sqlfiddle.com/#!9/6f936/1

now lets convert select update command , as

update users u left join (   select user_id,sum(score) total from(     select user_id, score table_1     union     select user_id, score table_2     union     select user_id, score table_3   )x group x.user_id )y on y.user_id = u.id set u.overall_score = coalesce(y.total,0) 

here demo http://www.sqlfiddle.com/#!9/c6993/1