I am trying to create my first trigger in postgres but I keep receiving this: [42883] ERROR: function clear_article_flag does not exist.
What I am trying to do is: when a new row is inserted on articles with a non 'automatic' author to set is_automatic flag to false for the specific id.
CREATE OR REPLACE FUNCTION clear_article_flag()
RETURNS trigger
LANGUAGE plpgsql AS
$$
BEGIN
update flags
set is_automatic = false where id= new.id;
return NEW;
END ;
$$;
CREATE TRIGGER maintain_dummy_flag
AFTER INSERT
ON articles
FOR EACH ROW
WHEN ( new.author not in ('automatic') )
EXECUTE PROCEDURE clear_article_flag();```
My mistake, being the first time when I've created a trigger and a sql function, I didn't know that first I should run the part that creates the function and then the trigger.
Related
I created a function that takes as a parameter a string by which i am looking for the desired element in the Bus table. After that i create a trigger that will fire after inserting into the Maintenance table. Here i have a problem: i specify that when changing the table, call the function and pass the last added element there, but the trigger is not created.
I looked for similar questions and saw that you need to take the query in brackets, but it did not help.
Ask for your help!
Function:
create function set_status(model_ varchar(50)) returns void as $$
update Bus set technical_condition = 'don`t work' where model = model_;
$$ LANGUAGE sql;
Trigger:
create trigger check_insert
after insert on Maintenance
for each row
execute procedure set_status((select model from Maintenance order by id_m desc limit 1));
First off your trigger function must be of the form:
create or replace function <function_name>()
returns trigger
language plpgsql
as $$
begin
...
end;
$$;
The language specification may come either before the code or after it. Moreover it must be defined returning trigger and as taking no parameters. See documentation.
You can achieve what you want by moving the select status ... query into the trigger function itself.
create or replace function set_status()
returns trigger
language plpgsql
as $$
begin
update bus
set technical_condition =
(select model
from maintenance
order by id_m desc
limit 1
) ;
return null;
end;
$$;
create trigger check_insert
after insert on maintenance
for each row
execute procedure set_status();
NOTE: Not Tested.
I created a table name Student in PostgreSQL and then I tried defining a trigger on that table but it's showing an error message in doing so.
Trigger Syntax:
CREATE TRIGGER bi_Student BEFORE INSERT ON Student as $$
FOR EACH ROW
BEGIN
raise notice 'Successfully inserted into table(%)', user;
end $$;
Table Creation Command:
create table Student(Stu_id int, Stu_Name text, Stu_Age int, Stu_address char(30));
Actually I tried to declare the execution statements directly inside the trigger only rather than calling any procedure/ function from the trigger which is working fine but I want to do in this way in PostgreSQL.
PostgreSQL doesn't support it. You need trigger function always.
As documented in the manual you need a trigger function
create function my_trigger_function()
returns trigger
as
$$
begin
raise notice 'Successfully inserted into table(%)', user;
return new; --<< important (see the manual for details)
end
$$
language plpgsql;
Not sure what you intend with the user parameter there, as that is not the table name, but the current database user. If you want to display the actual table name, you need to use TG_RELNAME instead - which is an implicit variable available in the trigger function.
And a trigger definition
CREATE TRIGGER bi_Student
BEFORE INSERT ON Student
FOR EACH ROW
execute function my_trigger_function();
The code below is my code to create trigger function to change column "pass".
create or replace function change_pass()
returns trigger as
$$
begin
NEW.pass := 'XXXXXXXXX';
return NEW;
end
$$
language plpgsql;
create trigger change_pass
AFTER insert or update on "D_ACCOUNT"
for each row execute procedure change_pass();
When i called insert, i did not see any changes in my data.
Can anyone explain to me where i was wrong?
You need a BEFORE trigger to change values in the NEW record:
create trigger change_pass
BEFORE insert or update on "D_ACCOUNT"
for each row execute procedure change_pass();
I have been trying to write a trigger function that updates the rows in the child table when the parent is changed for a while now.
I have read Trigger procedure documentation but i have not really grasped how to build the functions.
This is what I have tried that does not work...
CREATE FUNCTION myschema.update_child() RETURNS trigger AS
$BODY$
BEGIN
UPDATE myschema.child
set new.number = parent.number
FROM myschema.parent
WHERE id = "id";
RETURN NEW;
END
$BODY$
LANGUAGE plpgsql
Then the trigger
CREATE TRIGGER update_child_after_update
AFTER INSERT OR UPDATE OR DELETE
ON myschema.child
FOR EACH ROW
EXECUTE PROCEDURE myschema.update_child();
Does anyone have some tips to give?
Best regards
You don't need to use the parent table in the body of the trigger function, because the values from the parent table are available in the function in the special variable OLD and NEW. In this case you only need NEW.
If you need the trigger only on update, than define a update-only trigger:
CREATE or replace FUNCTION update_child() RETURNS trigger AS
$BODY$
BEGIN
UPDATE child
set number = NEW.number
WHERE id = NEW.id;
RETURN NEW;
END
$BODY$
LANGUAGE plpgsql;
CREATE TRIGGER update_child_after_update
AFTER UPDATE
ON parent
FOR EACH ROW
EXECUTE PROCEDURE update_child();
I know how to do this using SQL Server or Sybase, but can't seem to get it right using Postgres 9.4. I have a FUNCTION that is working as intended:
CREATE OR REPLACE FUNCTION "public"."welcome"(u_id INT DEFAULT 1234)
RETURNS "void"
AS $$
INSERT INTO my_table_1 (title,body,category,user_id,created_at)
VALUES ('Welcome!', '<some text>','general',u_id,now())
$$ LANGUAGE sql
This FUNCTION works as expected when called as SELECT welcome(1234);
However, what I'm trying to do is call or trigger this FUNCTION based on the condition AFTER a new user gets inserted into another table and that user is the first and only user:
INSERT INTO my_table_2 (user_id,name,...) VALUES (5678,'John Doe',...);
and the following condition is met:
SELECT COUNT(*) from my_table_2 WHERE <my conditions are met>;
returns exactly and only 1
So, symantically, I'm trying to accomplish:
call TRIGGER welcome(1234) AFTER INSERT into my_table_2 where my conditions are met
I've seen some examples, and don't quite understand the CREATE FUNCTION x() AS TRIGGER syntax, and it seems that Postgres is steering me in this direction, but examples are lacking in my case. Help! (and thanks in advance!)
In the SQL standard, you define a trigger that fires a trigger function when a certain action is taking place. In your case you want to create an AFTER INSERT trigger whose trigger function calls your "welcome" function.
First the trigger function:
CREATE FUNCTION call_welcome() RETURNS trigger AS $$
DECLARE
cnt integer;
BEGIN
SELECT count(*) INTO cnt FROM my_table_2 WHERE ...;
IF cnt = 1 THEN
PERFORM welcome(NEW.user_id);
END IF;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
And the trigger:
CREATE TRIGGER tr_call_welcome
AFTER INSERT ON my_table_2
FOR EACH ROW EXECUTE PROCEDURE call_welcome();