Postgres update join

update-join.sql

-- given two tables with a foreign key
-- and the requirement to set a field in tableA to the value of the corresponding field in tableB
-- in this case setting tableA.someField to tableB.someOtherField where tableA.fk_id = tableB.id

-- tableA (
-- id
-- someField
-- fk_id
-- )

-- tableB (
-- id
-- someOtherField
-- )


UPDATE tableA
SET someField = tableB.someOtherField
FROM tableB
WHERE tableA.fk_id = tableB.id;