Ottenere raccolte di date consecutive

Ok l'ho capito ed è stato abbastanza semplice, praticamente su ciascuno dei LEFT JOIN Ho dovuto filtrare la data di inizio in base ai parametri passati.

Ho anche dovuto filtrare in base al fatto che il congedo fosse approvato, un Approved_DateTime e Approved_By campo dove compilato se è stato approvato. Anche il calcolo della durata è stato un po' sbagliato in alcune circostanze. Quindi la mia procedura memorizzata ora è simile a:

DELIMITER $$

USE `test`$$

DROP PROCEDURE IF EXISTS `GetLeaveDates`$$

CREATE DEFINER=`root`@`%` PROCEDURE `GetLeaveDates`(pEmpID INT, pDateFrom DATETIME, pDateTo DATETIME, pApproved BOOLEAN)
BEGIN

SELECT 
    DATE_FORMAT(a.start_date,'%d/%m/%y') AS start,
CASE WHEN a.am_pm = 1 THEN "AM"
     WHEN a.am_pm = 2 THEN "PM"
     ELSE "" END AS start_am_pm,
    DATE_FORMAT(CASE WHEN pDateTo > MIN(c.start_date) THEN
        MIN(c.start_date)
    ELSE
        pDateTo
    END, '%d/%m/%y') AS end,
CASE WHEN c.am_pm = 1 THEN "AM"
     WHEN c.am_pm = 2 THEN "PM"
     ELSE "" END AS end_am_pm,
  CASE WHEN a.am_pm = 0 THEN
    CASE WHEN c.am_pm = 0 OR c.am_pm = 2 THEN
        DATEDIFF(MIN(c.start_date),a.start_date)+1
    WHEN c.am_pm = 1 THEN
        DATEDIFF(MIN(c.start_date),a.start_date)+0.5
    END
WHEN a.am_pm = 1 THEN
    CASE WHEN c.am_pm = 0 OR c.am_pm = 2 THEN
        DATEDIFF(MIN(c.start_date),a.start_date)+1
    WHEN c.am_pm = 1 THEN
        DATEDIFF(MIN(c.start_date),a.start_date)+0.5
    END
WHEN a.am_pm = 2 THEN
    CASE WHEN c.am_pm = 0 OR c.am_pm = 2 THEN
        DATEDIFF(MIN(c.start_date),a.start_date)+0.5
    WHEN c.am_pm = 1 THEN
        DATEDIFF(MIN(c.start_date),a.start_date)
    END 
END AS Duration

FROM t AS a
LEFT JOIN t AS b ON a.employee_id=b.employee_id AND a.start_date = ADDDATE(b.start_date,1) AND ISNULL(b.approved_datetime) <> pApproved AND b.start_date BETWEEN pDateFrom AND pDateTo
LEFT JOIN t AS c ON a.employee_id=c.employee_id AND a.start_date <= c.start_date AND ISNULL(c.approved_datetime) <> pApproved AND c.start_date BETWEEN pDateFrom AND pDateTo
LEFT JOIN t AS d ON c.employee_id=d.employee_id AND c.start_date = ADDDATE(d.start_date,-1) AND ISNULL(d.approved_datetime) <> pApproved AND d.start_date BETWEEN pDateFrom AND pDateTo
WHERE b.start_date IS NULL AND c.start_date IS NOT NULL AND d.start_date IS NULL
AND a.EMPLOYEE_ID = pEmpID
AND a.START_DATE BETWEEN pDateFrom AND pDateTo
AND ISNULL(a.approved_datetime) <> pApproved
AND a.start_date BETWEEN pDateFrom AND pDateTo
GROUP BY a.employee_id, a.start_date
; END$$

DELIMITER ;