Imagine I have these tables:

table_1:

    id   col_1  col_2 
     1   val_1  val_10 
     2   val_2  val_20

table_2:

    id   col_1  col_2
     1   val_3  val_30 
     3   val_4  val_40

I want to do an union of table_1 and table_2, removing duplicate ids, and selecting the values of table_2 over table_1 when an id is present in both tables.

union_result:

          id  col_1  col_2
          1   val_3  val_30
          2   val_2  val_20
          3   val_4  val_40

Both tables are massive (billions of records). What is the most efficient way to achieve this?

Thanks!