Question

I don’t know anything about stored procs. But desperately need one to run an update sql when a boolean column in a table changes value from false to true. If someone could provide one it will be greatly appreciated.

Thanks in advance

Answer 1

Here’s a test table

CREATE TABLE test20120524
(
  id integer NOT NULL,
  bool boolean,
  comment_by_trigger text,
  CONSTRAINT pk_test20120524 PRIMARY KEY (id)
)
WITH (
  OIDS=TRUE
);

This is a sample trigger function. OLD and NEW are pre-declared variables that means the updated row.

create or replace function test1() returns opaque as
'
declare
    -- some variables
begin
    if OLD.bool = false and NEW.bool = true then
        NEW.comment_by_trigger = ''affected by trigger'';
    end if;
    return NEW;
end;
' language 'plpgsql';

Then, create trigger.

CREATE TRIGGER test2
  BEFORE UPDATE
  ON test20120524
  FOR EACH ROW
  EXECUTE PROCEDURE test1();

Stored Procedures are not so difficult. You can learn it easily in PostgreSQL official documents : http://www.postgresql.org/docs/9.1/interactive/index.html

see

• 36.. Triggers
• 39.. PL/pgSQL – SQL Procedural Language (especially 39.9 Trigger Procedures)