Kompleks 'Gaps and Islands'-spørgsmål

Det er uklart, hvordan du bestemmer type for hver periode. Jeg valgte minimumsantallet.

Forudsat denne grundlæggende tabeldefinition:

CREATE TABLE tbl (person text, eventdate date, type int);
 

Grundlæggende foreslår jeg vinduefunktioner i to indlejrede underforespørgsler for at identificere medlemmer af samme periode (ø). Saml derefter:

SELECT person, period
     , min(eventdate) AS startdate
     , max(eventdate) AS enddate
     , count(*)       AS days
     , min(type)      AS type
FROM  (
   SELECT person, eventdate, type
        , count(gap) OVER (PARTITION BY person ORDER BY eventdate) AS period
   FROM  (
      SELECT person, eventdate, type
           , CASE WHEN lag(eventdate) OVER (PARTITION BY person ORDER BY eventdate)
                     > eventdate - 6  -- within 5 days
                  THEN NULL           -- same period
                  ELSE TRUE           -- next period
             END AS gap
      FROM   tbl
      ) sub
   ) sub
GROUP  BY person, period
ORDER  BY person, period;
 

Resultat (baseret på dine eksempeldata):