Very cool 9.5 feature

I was impressed by the ability of PostgresSQL to do this so I though I'd
share it with the group.

--CREATE TABLE db2 (a INT PRIMARY KEY, b TEXT,c text);

INSERT into db2 as current
SELECT * FROM json_populate_record(null::db2,
(SELECT '{"a":3,"b":"test3.2","c":"ctest3.2"}'::json))
on conflict (a) do update set b = coalesce(EXCLUDED.b,current.b),
c = coalesce(EXCLUDED.c,current.c)
;

INSERT into db2 as current
SELECT * FROM json_populate_record(null::db2,
(SELECT '{"a":3,"b":"test99"}'::json))
on conflict (a) do update set b = coalesce(EXCLUDED.b,current.b),
c = coalesce(EXCLUDED.c,current.c)
;

Note that the second insert will not UPDATE the value of column C to NULL
due to the "coalesce".
Very cool; maybe the next release will let us do:
"on conflict (a) DO UPDATE set ROW from NEW-VALUES".

Mike