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1CREATE OR REPLACE FUNCTION update_updated_at()
2  RETURNS TRIGGER AS $$
3  BEGIN
4      NEW.updated_at = now();
5      RETURN NEW;
6  END;
7  $$ language 'plpgsql';
8	
9CREATE TRIGGER update_users_updated_at
10  BEFORE UPDATE ON users
11  FOR EACH ROW EXECUTE PROCEDURE update_updated_at();
12	
13DROP TABLE mdt;
14
15CREATE TABLE mdt (
16    id      int4,
17    idesc       text,
18    moddate timestamp DEFAULT CURRENT_TIMESTAMP NOT NULL
19);
20
21CREATE TRIGGER mdt_moddatetime
22    BEFORE UPDATE ON mdt
23    FOR EACH ROW
24    EXECUTE PROCEDURE moddatetime (moddate);
25
26INSERT INTO mdt VALUES (1, 'first');
27INSERT INTO mdt VALUES (2, 'second');
28INSERT INTO mdt VALUES (3, 'third');
29
30SELECT * FROM mdt;
31
32UPDATE mdt SET id = 4
33    WHERE id = 1;
34UPDATE mdt SET id = 5
35    WHERE id = 2;
36UPDATE mdt SET id = 6
37    WHERE id = 3;
38
39SELECT * FROM mdt;
40	
41CREATE EXTENSION spi;
42
43ALTER TABLE users ALTER timestamp_at SET DEFAULT now();
44
45DROP TRIGGER IF EXISTS
46  update_users_updated_at ON users;
47
48CREATE TRIGGER mdt_users
49  BEFORE UPDATE ON users
50  FOR EACH ROW
51  EXECUTE PROCEDURE moddatetime (timestamp_at);