Postgres触发器会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2张桌子。一个与城市，一个与人。

城市：

大家：

我需要一个触发器，当表格中的“已处理”值从该城市的所有人更新为0时，表格城市中的“已处理”值从0更新为1.

例如：John，Ian和Claire来自柏林，每当“处理”值更新为1时，触发器会将表格城市中柏林的处理值更新为1。

最好的方法是什么？

Answer 1

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

alias c获取城市ID，然后为人们的sict id处理聚合，并且只有在处理完所有名称时才更新更新。

Answer 2

这将有效：

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();