PostgreSQL：创建触发器 [英] Postgresql: Creating a Trigger

问题描述

我必须在postgresql中创建一个触发器（没有任何函数调用）。我有两个表LivesIn（pid，名称，省）和Places（名称，省，人口，市长）

I have to create a trigger in postgresql (without any function calls). I have two tables LivesIn(pid, name, province) and Places(name, province, population, mayorid)

我有以下代码：

CREATE TRIGGER updatePopulation
AFTER INSERT ON LivesIn
FOR EACH ROW  
UPDATE Places
SET NEW.population = OLD.Population + 1
WHERE LivesIn.name = Places.name AND LiveIn.province = Places.province;

我遇到以下错误：
psql：/ home / 2008 / uehtes / Desktop /Comp421/comp421_a2_q1.sql:111：错误： UPDATE
或附近的语法错误第5行：UPDATE Places.population
^

I am getting the following error: psql:/home/2008/uehtes/Desktop/Comp421/comp421_a2_q1.sql:111: ERROR: syntax error at or near "UPDATE" LINE 5: UPDATE Places.population ^

任何帮助将非常感激。

Any help would be really appreciated.

推荐答案

@Glenn，显然不是这样做的方法。您必须创建一个函数并在触发器中调用它。像这样：

@Glenn, apparently that is not the way to do it. You have to create a function and call it in the trigger. Like this:

CREATE FUNCTION updatePop() RETURNS TRIGGER AS $updatePopulation$
DECLARE
    name1 varchar(30);
    name2 varchar(30);
BEGIN
    IF (TG_OP = 'INSERT') THEN
        name1 = NEW.name;
        name2 = NEW.province;
        UPDATE Place
        SET population = population + 1
        WHERE name1 = Place.name AND name2 = Place.province;
END IF;
RETURN NULL;    
END;
$updatePopulation$ LANGUAGE plpgsql;

CREATE TRIGGER updatePopulation
AFTER INSERT ON LivesIn
FOR EACH ROW 
EXECUTE PROCEDURE updatePop();

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