Sum up network events by type, interval and network

Hi all,

For each event of each type in each interval I want to compute the sum
of events referencing the same relayNet (via host) and insert/update 1
row in SumOfEvents.
All intervals start at a time, minimum 5 minutes in the past, rounded
down modulo 5 minutes like:

SELECT DATE_TRUNC('MINUTES', NOW () - ('0:' || (SELECT
(EXTRACT('MINUTE' FROM NOW())::INT % 5) + 5 ) || ':0')::INTERVAL);



CREATE TABLE host (  id            SERIAL  PRIMARY KEY,  relayNetFK    INT                REFERENCES relayNet
            ON DELETE CASCADE 
)

CREATE TABLE event (  id            SERIAL  PRIMARY KEY,  type          CHAR         NOT NULL                CHECK (
typeIN ('C', 'A', 'D', 'S', 'R') ),  timeOfEvent   timestamp       NOT NULL                        DEFAULT NOW(),
hostfk       INT          NOT NULL                REFERENCES host                        ON DELETE CASCADE 
)

CREATE TABLE relayNet (  id            SERIAL  PRIMARY KEY,  name          TEXT            NOT NULL UNIQUE
)

CREATE TYPE eventIntervals AS ENUM ('5m', '30m', '3h', '24h', '30d');
CREATE TABLE SumOfEvents (  id            SERIAL  PRIMARY KEY,  type          CHAR         NOT NULL
CHECK( type IN ('C', 'A', 'D', 'S', 'R') ),  startTime     timestamp       NOT NULL,  interval      eventIntervals  NOT
NULL, value         INT,        -- sum  relayNetFK    INT                REFERENCES relayNet                        ON
DELETECASCADE, 
  UNIQUE (type, interval, relayNetFK)
)

Can this be done w/o procedural code?
Any hints?

Thanks, Axel
---
axel.rau@chaos1.de  PGP-Key:29E99DD6  +49 151 2300 9283  computing @
chaos claudius