copy one column from one table to another

Question

I am confused about how to copy a column from one table to another table using where. I wrote SQL query but it says transaction lock time exceeded or query returns more than one row.
using mysql
Basically,
I have:

Table 1:  Results
BuildID  platform_to_insert

Table 2:  build
BuildID correct_platform

update results set results.platform_to_insert 
     = (select correct_platform from  
       build where results.BuildID = build.BuildID)

Answer 1

There are two options here:

1. update your tables to use BuildID as a primary key (to avoid duplicates)

2. update your subquery to only return one result

   UPDATE results SET results.platform_to_insert = (SELECT correct_platform FROM build WHERE results.BuildID=build.BuildID LIMIT 1);

Answer 2

I do not believe you need a sub query.

UPDATE results, build
SET    results.platform_to_insert = build.correct_platform
WHERE  results.BuildID = build.BuildID