关于postgresql timestamp时间戳问题

-- 创建触发函数 --
CREATE OR REPLACE FUNCTioN update_modified_column() 
RETURNS TRIGGER AS $$
BEGIN
    NEW.update_time = now();
    RETURN NEW; 
END;
$$ language 'plpgsql';
 
-- 创建触发器  on 后面是对应数据库的表名--
CREATE TRIGGER update_customer_modtime BEFORE UPDATE ON area FOR EACH ROW EXECUTE PROCEDURE  update_modified_column();

-- 查询所有触发器 --
SELECT * FROM pg_trigger;
-- 查询所有触发函数 --
select * from pg_proc;

select date_part('day', '2015-01-15 17:05'::timestamp - '2013-01-14 16:05'::timestamp);

select ('2015-01-15 17:05'::timestamp)::date - ('2015-01-14 19:05'::timestamp)::date;