Postgresql-Trigger erstellen, bevor eine Zeile

Question

Löschen

, so habe ich diese beiden Tabellen:

Table user 
columns: id,name,surname, password,token,earnedmoney 


Table addlisting 
columns: id, user_fk,price,date_added 

Hier ist mein Problem: Ich möchte einen Trigger erstellen, so dass, wenn ich einen Eintrag aus der addlisting Tabelle löschen, der Preis der Liste wird der Spalte "EarnedMoney" hinzugefügt, die in der Tabelle Benutzer ist.

Kann mir jemand helfen? Vielen Dank!

Answer 1

CREATE OR REPLACE FUNCTION add_money() RETURNS trigger AS 
$$BEGIN 
    UPDATE "user" SET earnedmoney = earnedmoney + OLD.price 
     WHERE id = OLD.user_fk; 
    RETURN OLD; 
END;$$ LANGUAGE plpgsql; 

CREATE TRIGGER add_money 
    BEFORE DELETE ON addlisting FOR EACH ROW 
    EXECUTE PROCEDURE add_money(); 

Es könnte auch ein AFTER Auslöser sein, die keinen Unterschied machen würde.

Answer 2

Nur regelmäßige erstellen BEFORE-Trigger DELETE:

test1=# create table addlisting (id serial PRIMARY KEY, user_fk integer, price float, date_entered date); 
CREATE TABLE 

test1=# insert into users (name, sername, password, token) values ('user1', '', '123', '123'), ('user2', '', '234', '234'); 
INSERT 0 2 

test1=# insert into addlisting (user_fk, price, date_entered) values (1, 100, now()), (1, 34, now()), (2, 465, now()); 
INSERT 0 3 

test1=# select * from users; 
id | name | sername | password | token | earnedmoney 
----+-------+---------+----------+-------+------------- 
    1 | user1 |   | 123  | 123 |    
    2 | user2 |   | 234  | 234 |    
(2 rows) 

test1=# select * from addlisting; 
id | user_fk | price | date_entered 
----+---------+-------+-------------- 
    1 |  1 | 100 | 2016-07-08 
    2 |  1 | 34 | 2016-07-08 
    3 |  2 | 465 | 2016-07-08 
(3 rows) 

test1=# CREATE OR REPLACE FUNCTION update_price() RETURNS trigger AS $emp_stamp$ 
test1$#  BEGIN 
test1$#   update users 
test1$#   set earnedmoney = coalesce(earnedmoney, 0) + coalesce(OLD.price, 0) 
test1$#   where id = OLD.user_fk; 
test1$# 
test1$#   return OLD; 
test1$#  END; 
test1$# $emp_stamp$ LANGUAGE plpgsql; 
CREATE FUNCTION 

test1=# CREATE TRIGGER on_delete_addlisting 
test1-# BEFORE DELETE ON addlisting 
test1-#  FOR EACH ROW EXECUTE PROCEDURE update_price(); 
CREATE TRIGGER 

Test:

test1=# delete from addlisting where id in (1,3);      
DELETE 2 

test1=# select * from addlisting; 

id | user_fk | price | date_entered 
----+---------+-------+-------------- 
    2 |  1 | 34 | 2016-07-08 
(1 row) 

test1=# select *from users;    
id | name | sername | password | token | earnedmoney 
----+-------+---------+----------+-------+------------- 
    1 | user1 |   | 123  | 123 |   100 
    2 | user2 |   | 234  | 234 |   465 
(2 rows) 


test1=# delete from addlisting; 
DELETE 1 

test1=# select *from users; 
id | name | sername | password | token | earnedmoney 
----+-------+---------+----------+-------+------------- 
    2 | user2 |   | 234  | 234 |   465 
    1 | user1 |   | 123  | 123 |   134 
(2 rows)