288Lg8eU

1CREATE TABLE IF NOT EXISTS devices(
2  device_id serial PRIMARY KEY,
3  device_name varchar(255) UNIQUE NOT NULL,
4  last_record_time timestamp without time zone NOT NULL DEFAULT '1995-10-30 10:30:00'
5);
6
7CREATE TABLE IF NOT EXISTS temperature(
8  device_id integer NOT NULL,
9  temperature decimal NOT NULL,
10  record_time timestamp without time zone,
11  CONSTRAINT temperature_device_id_fkey FOREIGN KEY (device_id)
12    REFERENCES devices (device_id) MATCH SIMPLE
13    ON UPDATE NO ACTION ON DELETE NO ACTION
14);
15	
16SELECT MAX(record_time) FROM temperature WHERE device_id=4;