Problem: I have an Aurora RDS database that has a table where the data for a certain column was deleted. I have a snapshot of the DB from a few days ago that I want to use to populate the said column with the values from the snapshot. The issue is that certain rows have been deleted from the live DB in the meantime and I don't want to include them again.
I want to mount the snapshot, connect to it and then SELECT INTO OUTFILE S3 the table that interests me. Then I will LOAD DATA FROM S3 into the live DB, selecting only the column that interests me. But I haven't found information about what happens if the number of rows differ, namely if the snapshot has rows that were deleted in the meantime from the live DB.
Does the import command take the ID column into consideration when doing the import? Should I also import the ID column? I don't want to recreate the rows in question, I only want to populate the existing rows with the values from the column I want from the snapshot.
ALTER TABLE the destination table to add the column you are missing. It will be empty of data for now.
LOAD DATA your export into a different table than the ultimate destination table.
Then do an UPDATE with a JOIN between the destination table and the imported table. In this update, copy the values for the column you're trying to restore.
By using an inner join, it will only match rows that exist in both tables.