MySQL：使用一个表快速填充另一个表(MySQL: Use one table to fill another quickly)

 我正在运行MySQL（对我而言是新语言），并且正在尝试合并两个表，如此论坛上所描述的那样令人作呕。 我从另一个线程中获取了似乎最受欢迎的答案，并且它有效： 
 
  ALTER TABLE table1 ADD col3 varchar( 30 ) NOT NULL; 
  UPDATE table1,table2
  SET table1.col3=table2.col3
  WHERE table1.col1 = table2.col1 AND table1.col2 = table2.col2
 
 问题是性能 - 这需要15秒来更新500条记录，显然需要几个小时来更新~50k记录（在我的Macbook上）。 我怎样才能让这个更快？ 

I am running MySQL (new language for me) and am trying to merge two tables as described ad nauseam on this forum. I took what seems to be the most popular answer from another thread, and it works:
 
  ALTER TABLE table1 ADD col3 varchar( 30 ) NOT NULL; 
  UPDATE table1,table2
  SET table1.col3=table2.col3
  WHERE table1.col1 = table2.col1 AND table1.col2 = table2.col2
 
The problem is performance -- this takes 15 s to update 500 records, and apparently hours to update ~50k records (on my Macbook). How can I make this MUCH faster?

原文：https://stackoverflow.com/questions/36050912