MySQL: Changing IDs of primary keys

Question

I need to merge parallel tables from 2 different schemas. They are practically the same (some fields are different), but the IDs (their PKs) are different.

I need to conform one table to contain the same IDs for the parallel rows. (both tables continue to live after the merge, and one is synched to the other according to the IDs)

What is the best way to go about it?

• Renaming the IDs of the first table according to the second one, and then changing the auto_increment value of the PK?

• Creating a temporary table with the needed values inserted with the correct IDs, and then removing the original and renaming the temp?

• Is there a better way?

Besides, how can this affect indexes?

does it have any other reprocussions? (besides foreign_keys and places in the code - if exist - using hardcoded ID values)

Answer 1

1. Don't think you have an option. You have to generate new ids. When you insert records the auto_increment would anyway happen.
2. You can have an additional column reference which can have the original table key value to back trace.
3. PK indexes will be re-indexed.

Other repercussions depend on the app functionality which you have to consider.