Mysql
 sql >> Datenbank >  >> RDS >> Mysql

SQL-Anfrage, um festzustellen, ob ein Zeitraum vollständig abgedeckt ist

BEARBEITEN: Sehen Sie hier für eine MySQL funktionierende SQL Fiddle:SQLFiddle , das funktioniert diesmal tatsächlich richtig :-)

Probiere diese. Die Quintessenz ist, dass wenn Shortfall > 0 dann können Sie die Miete nicht buchen.

MSSQL - So habe ich es ausgearbeitet

DECLARE @start DATETIME = '2013-04-29' -- this will depend on your dateformat
DECLARE @end DATETIME = '2013-05-10'
DECLARE @days INT = DATEDIFF(D,@start, @end) -- this is how many days we actually want to stay
DECLARE @unusedDays INT = 0 -- this will be the number of unused days from the rental periods in which our start and end dates fall
SELECT  @UnusedDays = DATEDIFF(D,@end,end_at) FROM PERIODS WHERE (@end > start_at AND @end <= end_at) -- how many spare days are there in the final period?
SELECT  @UnusedDays = @UnusedDays + DATEDIFF(D,start_at, @start) FROM PERIODS WHERE (@start >= start_at AND @start < end_at) -- how many spare days are there in the start period?
SELECT  @days + @UnusedDays - SUM(DATEDIFF(D,start_at,end_at)) AS Shortfall, -- total shortfall in days. Zero if we are okay to rent
        SUM(DATEDIFF(D,start_at,end_at)) AS AvailableDays, -- total number of days available in all periods covering our chosen rental period
        @days AS DesiredDays, -- number of days we want to rent
        @UnusedDays AS WastedDays -- number of wasted days (if we start or end our rental mid-period)
FROM    PERIODS 
WHERE   (@start >= start_at AND @start < end_at) -- period in which our selected rental starts
OR      (end_at < @end AND start_at > @start) -- period completely within our selected rental
OR      (@end > start_at AND @end <= end_at) -- period in which our selected rental ends

Dies liefert eine Ausgabe wie diese:

-- if you have @start = '2013-05-05'
-- and @end = '2013-05-13'
-- then you get
Shortfall AvailableDays DesiredDays WastedDays

0---------10------------8-----------2---------

-- if you have @start = '2013-04-29'
-- and @end = '2013-05-10'
-- then you get
Shortfall AvailableDays DesiredDays WastedDays

5---------6-------------11----------0---------

MySQL - das ist es, was Sie wirklich wollen

SET @start = '2013-04-29';
SET @end = '2013-05-10';
SET @days = DATEDIFF(@end, @start); -- this is how many days we actually want to stay
SET @UnusedDays = 0; -- this will be the number of unused days from the rental periods in which our start and end dates fall
SELECT  @UnusedDays := DATEDIFF(end_at,@end) FROM PERIODS WHERE (@end > start_at AND @end <= end_at); -- how many spare days are there in the final period?
SELECT 'hello';
SELECT  @UnusedDays := @UnusedDays + DATEDIFF(@start, start_at) FROM PERIODS WHERE (@start >= start_at AND @start < end_at); -- how many spare days are there in the start period?
SELECT 'hello';
SELECT  @days + @UnusedDays - SUM(DATEDIFF(end_at, start_at)) AS Shortfall, -- total shortfall in days. Zero if we are okay to rent
        SUM(DATEDIFF(end_at, start_at)) AS AvailableDays, -- total number of days available in all periods covering our chosen rental period
        @days AS DesiredDays, -- number of days we want to rent
        @UnusedDays AS WastedDays -- number of wasted days (if we start or end our rental mid-period)
FROM    PERIODS 
WHERE   (@start >= start_at AND @start < end_at) -- period in which our selected rental starts
OR      (end_at < @end AND start_at > @start) -- period completely within our selected rental
OR      (@end > start_at AND @end <= end_at); -- period in which our selected rental ends