How to UPSERT (MERGE, INSERT … ON DUPLICATE UPDATE) in PostgreSQL?

Question

A very frequently asked question here is how to do an upsert, which is what MySQL calls INSERT ... ON DUPLICATE UPDATE and the standard supports as part of the

Answer 1

Here are some examples for insert ... on conflict ... (pg 9.5+) :

• Insert, on conflict - do nothing.

  insert into dummy(id, name, size) values(1, 'new_name', 3)
  on conflict do nothing;`  
  

• Insert, on conflict - do update, specify conflict target via column.

  insert into dummy(id, name, size) values(1, 'new_name', 3)
  on conflict(id)
  do update set name = 'new_name', size = 3;  
  

• Insert, on conflict - do update, specify conflict target via constraint name.

  insert into dummy(id, name, size) values(1, 'new_name', 3)
  on conflict on constraint dummy_pkey
  do update set name = 'new_name', size = 4;