Question

A postgresql 9.1 DB writes data which is sent automatically from a machine. This works fine.

I have an AFTER INSERT …FOR EACH ROW trigger – this also works.
The trigger works by looking at another table and if there is a value in a field it fires.

I have two problems –
a. Some machines send more than 1 result. I am using LIMIT 1 to prevent duplicates and this means that I miss data from a machine that sends more than one result. What is an alternative to this?
b. Some machines share the same test code and I can`t find a way of qualifying this, to make it machine specific in the SELECT when I use the NEW value. Here is the code

CREATE FUNCTION testcode_matches()
    RETURNS TRIGGER as $$
DECLARE
    var INTEGER;
    name text;
    short text;
    id integer;
BEGIN
    SELECT count("TestID") from testcode WHERE "testcode"."Parameter" = NEW."Parameter" into var;
    IF var > 0 THEN
        SELECT "TestName", "ShortTestName", "TestID" 
        from testcode where "Parameter" = NEW."Parameter" Limit 1 into name, short, id;

        INSERT INTO finaldata /* various fields */
        SELECT /* various fields */ name, short, id
        from obx 
        WHERE "obx"."Parameter" = NEW."Parameter"
        LIMIT 1;
    END if;
    RETURN NEW;
END;
$$ language plpgsql;

Answer 1

Plain-SQL version, without all the variable stuff. (unknown details omitted or guessed) (untested)

CREATE FUNCTION testcode_matches()
    RETURNS TRIGGER as $meat$
BEGIN

    INSERT INTO finaldata ( name, short, id /* various fields */ )
    SELECT tc.name, tc.shorttestname, tc.id /* various fields */
    FROM testcode tc
    JOIN obx ON obx.parameter = tc.parameter
    WHERE tc.parameter = NEW.parameter
    AND tc.id = NEW.id -- is this the PK for testcode ??
                ;
    RETURN NEW;
END;
$meat$ language sql;

UPDATE:

set search_path='tmp';

DROP TABLE obx CASCADE;
CREATE TABLE obx
        ( parameter INTEGER NOT NULL PRIMARY KEY
        );

DROP TABLE testcode CASCADE;
CREATE TABLE testcode
        ( ID INTEGER NOT NULL PRIMARY KEY
        , parameter INTEGER NOT NULL  REFERENCES obx(parameter)
        , zname VARCHAR
        , shorttestname VARCHAR
        );

DROP TABLE finaldata CASCADE;
CREATE TABLE finaldata
        ( ID INTEGER NOT NULL PRIMARY KEY
        , zname VARCHAR
        , shorttestname VARCHAR
        );


DROP FUNCTION testcode_matches();
CREATE FUNCTION testcode_matches()
    RETURNS TRIGGER
    AS $meat$
BEGIN

    INSERT INTO finaldata ( id, zname, shorttestname /* various fields */ )
    SELECT tc.id, tc.zname, tc.shorttestname /* various fields */
    FROM testcode tc
    JOIN obx ON obx.parameter = tc.parameter
    WHERE tc.parameter = NEW.parameter
    AND tc.id = NEW.id -- is this the PK for testcode ??
                ;
    RETURN NEW;
END;
$meat$ language plpgsql;

DROP TRIGGER testcode_ins;
CREATE TRIGGER testcode_ins
        AFTER INSERT ON testcode
        FOR EACH ROW
        EXECUTE PROCEDURE testcode_matches()
        ;