Well say I have two physically separate database and I wish to replace database B with data from A. Except that I wish to keep the data in B which does not exist in A?
So basically I'd go over each entry in A and use an insert-or-replace like:
INSERT INTO table_name (name, value) VALUES ('hello', 'world') ON CONFLICT (name) do nothing;
IE the following databases would be merged into the third:
A) name | value A | 1 B | 2 B) name | value B | 10 C | 20 MERGED) name | value A | 1 B | 2 C | 20
If I use the
-c option from
pg_dump it would just throw away the "c" value in the merged table.