What you have written is a stored procedure not a trigger function. Trigger functions until 7.2 return generally OPAQUE and after 7.2 they return TRIGGER. See the example of a trigger below for your function
CREATE OR REPLACE FUNCTION customer_bak_proc() RETURNS TRIGGER AS '
BEGIN
IF TG_OP = ''DELETE'' THEN
INSERT INTO customer_bak (id,name,value) VALUES (OLD.id,OLD.name,OLD.value);
RETURN NULL;
END IF;
IF TG_OP = ''UPDATE'' THEN
INSERT INTO customer_bak (id,name,value) VALUES (NEW.id,NEW.name,NEW.value);
RETURN NEW;
END IF;
RETURN NULL;
END;' LANGUAGE 'plpgsql';
CREATE TRIGGER customer_bak_trigger AFTER DELETE OR UPDATE ON customers FOR EACH ROW EXECUTE PROCEDURE customer_bak_proc();
What happens above is create the function then create the trigger on the table and call the function based on what action occurred.
The function is in PL/PGSQL and it basically checks which operation and then checks the OLD array if it is a delete operation or the NEW array if it is an update operation.
NEW / OLD will hold all of the variables in the row that you just updated / deleted and will access them via name and the dot (.) operator.
HTH Darren
Barbara Lindsey wrote:
I am a postgres newbie.
I am trying to create a trigger that will put a copy of a record into a backup table before update or delete. As I understand it, in order to do this I must have a function created to do this task. The function I am trying to create is as follows:
CREATE FUNCTION customer_bak_proc(integer) RETURNS boolean as 'INSERT INTO customer_bak (SELECT * from customer where id = $1 )' LANGUAGE 'SQL';
Whenever I try to create this function, I get an error on the return type, as follows: ERROR: function declared to return boolean, but final statement is not a SELECT
I have tried using text, integer, opaque, NULL, 0, 1. And I have tried omitting the "RETURNS" clause altogether, but none of these works.
What is the return data type of an SQL INSERT statement? I think that would work (?), but I have not been able to find this in any of the documentation.
Has anyone else successfully written a function to do an insert? Has anyone else written a trigger to accomplish this kind of task? Perhaps I am taking the wrong approach... Thank you for any help. Barb Lindsey
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