Postgres 16

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CREATE TABLE main (
  "Id" INTEGER,
  "val" VARCHAR(7),
  "updated" VARCHAR(4)
);

INSERT INTO main
  ("Id", "val", "updated")
VALUES
  ('1', 'Value 5', 'null'),
  ('1', 'Value 5', 'null'),
  ('2', 'Value 8', 'null'),
  ('2', 'Value 8', 'null'),
  ('3', 'Value 3', 'null');

CREATE TABLE



INSERT 0 5


CREATE TABLE stg (
  "Id" INTEGER,
  "val" VARCHAR(7),
  "updated" VARCHAR(4)
);

INSERT INTO stg
  ("Id", "val", "updated")
VALUES
  ('1', 'Value 1', 'null'),
  ('2', 'Value 2', 'null'),
  ('3', 'Value 3', 'null'),
  ('3', 'Value 3', 'null'),
  ('4', 'Value 4', 'null');

CREATE TABLE



INSERT 0 5


UPDATE main m
SET "val" = s."val" , "updated" = s."updated"
FROM (SELECT DISTINCT "Id", "val", "updated" FROM  stg) s
WHERE s."Id" = m."Id"

UPDATE 5


SELECT * FROM main


Id
val
updated


1
Value 1
null

1
Value 1
null

2
Value 2
null

2
Value 2
null

3
Value 3
null



SELECT 5

Id	val	updated
1	Value 1	null
1	Value 1	null
2	Value 2	null
2	Value 2	null
3	Value 3	null