Postgres触发器，影响具有特定值的行

Question

我是postgres新手，我有一个关于触发器的问题。可以说我们有两张桌子。一个与城市，一个与人。

城市：

人物：

我需要一个触发表明更新 '处理' 在表城市从0到1的值，当在表 '处理' 值所有来自该城市的人都会从0更新为1。

例如：约翰，Ian和克莱尔来自柏林和当“处理”值更新为1为他们每个人，然后触发更新处理，柏林表城市1.

值是什么做到这一点的最佳方式？

Answer 1

这将工作：

CREATE OR REPLACE FUNCTION mytrigger() RETURNS TRIGGER AS $mytrigger$ 
    BEGIN 
     IF (SELECT EXISTS (SELECT 1 FROM PEOPLE WHERE city_id = NEW.city_id AND processed = '0')) THEN 
      UPDATE CITIES SET processed = '0' WHERE id = NEW.city_id; 
      RETURN NEW; 
     ELSE 
      UPDATE CITIES SET processed = '1' WHERE id = NEW.city_id; 
      RETURN NEW; 
     END IF; 
    END; 
$mytrigger$ LANGUAGE plpgsql; 

CREATE TRIGGER mytrigger 
AFTER UPDATE ON PEOPLE 
    FOR EACH ROW EXECUTE PROCEDURE mytrigger(); 

Answer 2

尝试此查询：

with c as (
    select city_id 
    from people 
    where name = NEW.name 
) 
, a as (
select avg(processed) 
from people 
join c on c.city_id = people.city_id 
) 
update cities u 
set processed = 1 
from a 
where u.id = a.city_id 
and avg = 1 

别名Ç得到城市的ID，然后在人，最后更新的更新，SICT ID，只有当所有的名字被处理加工的聚集。