On Wed, 13 Dec 2006, Erik Jones wrote:
Marc Evans wrote:
Hi -
I am struggling with a trigger function in plpgsql, and am hoping that
someone on this list can't show me a way to do what I need.
In the trigger, TG_ARGV[0] is the name of a column that I want to evaluate.
This code shows the concept, though is not functional:
CREATE OR REPLACE FUNCTION foo() RETURNS TRIGGER AS $$
DECLARE
column_name TEXT := TG_ARGV[0];
data TEXT;
BEGIN
EXECUTE 'SELECT NEW.' || column_name INTO data;
-- ...
END;
$$ LANGUAGE plpgsql;
When I try to use that code, I receive:
c3i=> insert into test_table values (1,1);
ERROR: NEW used in query that is not in a rule
CONTEXT: SQL statement "SELECT NEW.magic"
How can I get the value of NEW.{column_name} (aka NEW.magic in this
specific test case) into the variable data?
EXECUTE 'SELECT ' || NEW.column_name ';' INTO data;
Thanks for the suggestion. Unfortunately, it does not work:
CREATE OR REPLACE FUNCTION foo() RETURNS TRIGGER AS $$
DECLARE
column_name TEXT := TG_ARGV[0];
data TEXT;
BEGIN
EXECUTE 'SELECT ' || NEW.column_name || ';' INTO date;
-- ...
END;
$$ LANGUAGE plpgsql;
c3i=> insert into test_table values (1,1);
ERROR: record "new" has no field "column_name"
- Marc
