Hi I am trying to figure out the syntax for triggers. I have two tables one called tagged_in and the other notification. So I want to make a trigger where when an insert is called in tagged_in I want to insert a tuple in notification.
The manuals are available at the DB2 InfoCenter. Did you read the CREATE TRIGGER statement information yet? If not, why not? If so, what did you try, and what error did you get?
Something like this
CREATE TRIGGER TEST_TRIGGER
AFTER INSERT ON TAGGED_IN
REFERENCING NEW AS NEW_TAG
FOR EACH ROW
BEGIN ATOMIC
INSERT INTO NOTIFICATION
VALUES (NEW_TAG.FIELD1,NEW_TAG.FIELD2);
END
Related
I am new to PostgreSQL and I am currently working on triggers but am stuck at one point.
I have two tables Student and Room.
Room id is the primary key in Room and foreign key in Student.
If I am inserting in Student, then it should check in Room whether the new data exist or not.
This is a foreign key check constraint. I hope anyone can help me with it
I dont know your code and I dont get the meaning, but I can answer generally.
In PostgreSQL a trigger is normally defined in two steps:
Define a trigger function using the CREATE FUNCTION
Bind this created trigger function to a table using CREATE TRIGGER
A trigger function is a common function, except that is has a return value type trigger (in addition, it does not take any arguments).
CREATE OR REPLACE FUNCTION trigger_function()
RETURNS trigger
AS $$ ... $$;
binding:
CREATE TRIGGER trigger_name
AFTER INSERT ON table_name
FOR EACH ROW EXECUTE PROCEDURE trigger_function();
In addition, please also consult the excellent PG documentation at PostgreSQL 9.4 Triggers
I want to call a certain procedure that logs everytime a database user is created or deleted in the db ( sql Anywhere 16).
For this i have written a Function that should be called via a trigger when a row is inserted or deleted from table SYS.SYSUSER.
However, I am not able to create a trigger on this table.
Am i allowed to create trigger on this or is there someother way to get notified whenever a user is created or deleted for db?
New to sybase please help.
heres is my create trigger code
CREATE TRIGGER myTrigger AFTER INSERT ON sys.sysuser
REFERENCING NEW AS newRecord
FOR EACH ROW
BEGIN
--
END;
You cannot create a trigger on a system table. You can create a handler for "system events", which are described in the online SQL Anywhere documentation. Unfortunately, creation or deletion of users is not a system event that can be handled. I don't believe there's a way short of polling that you can do what you want to do.
Full disclosure: I work for SAP in SQL Anywhere engineering.
Sorry but I'm struggling with the online documentation.
What exactly is the difference for a FOR trigger compared to a AFTER and INSTEAD OF?
Thanks
The FOR and the AFTER trigger is the same. You specify them in the same way and they do the same thing:
CREATE TRIGGER sometrigger on sometable FOR INSERT,UPDATE,DELETE
CREATE TRIGGER sometrigger on sometable AFTER INSERT,UPDATE,DELETE
The INSTEAD OF trigger is something completely different. When you specify a trigger with the instead of then the trigger will execute instead of the insert, update and delete. This can be useful when you have views. So you can control what should be delete, updated and inserted in the views underlying tables
Here is an link to explain the triggers in more depth
I would like to know if a trigger on a system table of PostgreSQL can be executed when I create a table
I need to add 2 functions on each table of my database and I would like to do it dynamically
Thanks
This can be done with an event trigger:
CREATE OR REPLACE FUNCTION on_create_table_func()
RETURNS event_trigger AS $$
BEGIN
-- your code here
END
$$
LANGUAGE plpgsql;
CREATE EVENT TRIGGER
on_create_table ON ddl_command_end
WHEN TAG IN ('CREATE TABLE')
EXECUTE PROCEDURE on_create_table_func();
Note that there is no way to directly execute any query on the newly created table, or even get its name.
I don't know what you mean by "add 2 functions on each table" since functions don't belong to a specific table, but if you need to perform an operation specific for the new tables, this might not be for you.
I know it's an old question but now it has been implemented in version 9.3, or at least partially
http://www.postgresql.org/docs/9.3/static/event-trigger-definition.html
You're looking for "DDL Triggers". They're not implemented in PostgreSQL. Neither you can add triggers to system tables. Look at this forum entry:
Adding ddl audit trigger
How do I only create a trigger if it does not exist?
When I do create or replace, I get a syntax error so I am looking for a way to test for the existence of a trigger.
I can always select * from pg_trigger, but I am sure there is a more suitable way.
Thanks
Postgres can conditionally drop a trigger - see the docs. Do this before creating the trigger, then it will always work.
DROP TRIGGER IF EXISTS mytrigger ON mytable;
As Jack points out in the comments, this feature has only been available since 8.2; this has been out for more than four years though, so it should be available in your version.
CREATE TRIGGER (NameOfTrigger) AFTER INSERT OR UPDATE ON (NameOfTable)
DROP TRIGGER IF EXISTS (NameOfTrigger) ON (NameOfTable);