Question

maybe someone could shed some light on the statement that I have been battling with the entire day 🙂

I have 3 tables

Holiday

holidayID | userID | dateFrom   | dateTo
1         |      1 | 2012-01-01 | 2012-01-01
2         |      1 | 2012-01-15 | 2012-01-20

Status

statusID | holidayID | statusText
1        |         1 | accepted
2        |         2 | declined

UserSettings

id | userID | HolidaysAllowed
1  |      1 | 20

What I am trying to do is get the following result

Result

HolidaysAllowed | HolidaysLeft (Allowed - Taken) | HolidaysTaken (Sum of Holidays)
20              |                             19 |      1

I am able to get all three columns if I dont state a status – here is the closest I got

SELECT 
IFNULL(SUM( IF(  h.dateTo = h.dateFrom, 1, DATEDIFF( h.dateTo, h.dateFrom ) ) ), 0) AS holidaysTaken, 
IFNULL(us.HolidaysAllowed - ( SUM(  IF(  h.DateTo = h.DateFrom, 1, DATEDIFF( h.DateTo, h.dateFrom ) ) ) ), 0) AS holidaysLeftover, 
us.HolidaysAllowed
FROM userSettings us 
LEFT JOIN holiday h 
ON h.userID = 1 
JOIN status s 
ON s.holidayID = h.holidayID AND s.statusID = 1 
WHERE 
us.userID = 1
GROUP BY h.userID;

The main problem is that if there is no holiday with statusID = 2 then result column 1 & 2 are 0 (which is correct) but column 3 (HolidaysAllowed) is NULL (incorrect as it needs to always return the value from the table UserSettings). The above query only returns a correct response when there is at least 1 record (holiday) with the correct status… what am I doing wrong? 🙂

Its just driving me nuts 🙂 Thanks in advance for any help! Much appreciated!

UPDATE

Thanks to everyone who commented… the expected result is as follows
Get all holidays that have a status = 1 (i.e accepted) then calculate the holidays statistics against that of the holidays allowed. I.e.

20 days in total, 1 holiday accepted = 19 days left to take

thanks again

Answer 1

SELECT u.userID, u.HolidaysAllowed,
u.holidaysAllowed - 
COALESCE( 
    (SELECT SUM( DATEDIFF( h1.dateTo, h1.dateFrom) + 1) 
         FROM holiday h1 
         INNER JOIN status s1
         ON s1.holidayID = h1.holidayID
         WHERE h1.userID = u.userID
         AND s1.statusID = 1
     ), 0) AS HolidaysLeft,
COALESCE( 
    (SELECT SUM( DATEDIFF( h2.dateTo, h2.dateFrom) + 1) 
         FROM holiday h2 
         INNER JOIN status s2
         ON s2.holidayID = h2.holidayID
         WHERE h2.userID = u.userID
         AND s2.statusID = 1
     ), 0) AS HolidaysTaken
FROM userSettings u
;