How to migrate data to one table to another in MySQL

Question

I've two same tables(same table columns and primary key) in two different databases. I want to add 2nd table data to the first table that not exist in the first table (according to the primary key). what is the best method to do that?

I can export 2nd table data as csv, php array or sql file.

Thanks

Answer 1

There are lots of ways to do this.

The simplest is probably this one:

INSERT IGNORE
  INTO table_1 
SELECT *
  FROM table_2
     ;

which allows those rows in table_1 to supersede those in table_2 that have a matching primary key, while still inserting rows with new primary keys.

Alternatively, you can use a subquery to find out the rows that are not shared by both tables and insert them. If you've got a lot of records, you may want to consider using a temporary table to speed up the process.