Postgres 13

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CREATE TABLE foo (bar int, foo_bar text);
INSERT INTO foo (bar) VALUES (1),(2),(3);
3 rows affected

UPDATE foo SET foo_bar = 
  CASE 
    WHEN bar = 1 THEN 'dog' 
	WHEN bar = 2 THEN 'cat'
	WHEN bar = 3 THEN 'elephant'
  END;
3 rows affected

SELECT * FROM foo;


bar
foo_bar


1
dog

2
cat

3
elephant