faster way to write INNER JOIN function

Question

MySQL: I'm trying to add some data to my table from another table, where their id is the same.

update sf_leads t1
inner join temp_geninfo t2 
on t1.application_id = t2.application_id
set t1.org_city = t2.org_city;

However, each table has 92,000 values, and this query has been taking nearly an hour to finish. Is there a faster way to do this, or do I just need to wait?

Answer 1

For this query:

update sf_leads t1 inner join
       temp_geninfo t2 
       on t1.application_id = t2.application_id
    set t1.org_city = t2.org_city;

You want an index on temp_geninfo(application_id, org_city) :

create index idx_temp_geninfo_application_id_org_city on temp_geninfo(application_id, org_city);

You also might want to check that you don't have multiple updates on the same row, by running:

select application_id, count(*)
from temp_geninfo
group by application_id
having count(*) > 1;

If this returns any rows, then you potentially have the problem of the join multiplying the number of rows being updated.