Storing Schedule Information - sql

Question

I need to create a table to hold a schedule for meetings.
A meeting can be scheduled to be:
Daily
'Ever X days'. where X can be between 1 and 6.
Ending after X sessions. Where 'sessions' is basically the number of repeats.
Weekly
Which days during the week it can occur. Mon, Tue, etc. Can select more than one day per week.
The Date on which it ends.
Monthly
Use can select the day of the month it can occur (1st, 2nd etc)
OR they can select from a lookup of '1st, 2nd, 3rd, 4th or Last' and a Day 'Mon, Tues', saying, for example "The 2nd Friday" of the month.
How can I store all these scenarios in a single table?
I was thinking:
CREATE TABLE schedule
(
ID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
StartDate DATETIME NOT NULL,
EndTime TIME NULL,
RepeatTypeID INT NOT NULL, // Daily, Weekly, Monthly, None
// For Daily
EveryDayCount INT NULL, // to handle 'every 3 days',
RepeatCount INT NULL, // How many occurances. Can be shared with different RepeatTypes
// weekly
IsMonday BIT,
IsTuesday BIT,
etc // A field per day selection. Is there a better way?
// Monthly
MonthlyDayNumber INT NULL,
MonthlyRepeatIntervalID INT, // Lookup table with '1st, 2nd, 3rd, 4th, Last'
MonthlyDayRepeatSelection INT // Lookup on Monday, Tuesday etc
)
But this seems inefficient. Is there a better design pattern for these sorts of requirements?

Answer 1

So basically I once implemented the same functionality and I found that rather than ease of storage, that ease of retrieval and edit/update was of paramount importance.
You don't want to calculate all dates every single time, you query the DB for meeting dates or say like you have a function like showAllMeetingsForADate(somedate date) then you would not want to calculate dates for meeting at run time.
Holistically the most optimal storage is that you store meeting information calculation logic in a table and all meeting dates in another table like below.
However for the storage of meeting information, you should go with a normalized form.
Schedule Detail Tables
CREATE TABLE DailyScheduleDetails
(
ScheduleDetailsID INT PRIMARY KEY IDENTITY(1,1),
RecurrenceCount INT NOT NULL
)
CREATE TABLE WeeklyScheduleDetails
(
ScheduleDetailsID INT PRIMARY KEY IDENTITY(1,1),
OnMonday bit,
OnTuesday bit,
OnWednesday bit,
-- ...
OnSunday bit,
EndByDate Date NOT NULL
)
CREATE TABLE MonthlyScheduleDetails
(
ScheduleDetailsID INT PRIMARY KEY IDENTITY(1,1),
MonthlyDayNumber INT NULL,
MonthlyRepeatIntervalID INT, // Lookup table with '1st, 2nd, 3rd, 4th, Last'
-- Here I'd suggest using 0 for Last
MonthlyDayRepeatSelection INT // Lookup on Monday, Tuesday etc
)
Schedule
CREATE TABLE schedule
(
ID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
StartDateTime DATETIME NOT NULL,
EndDateTime DATETIME NULL,
RepeatTypeID INT NOT NULL, // Daily, Weekly, Monthly, None
ScheduleDetailsID INT
)
MeetingDates
CREATE TABLE MeetingDates
(
ID INT NOT NULL PRIMARY KEY IDENTITY(1,1),
MeetingID int,
MeetingStartDate datetime,
MeetingEndDate datetime -- because you can have meeting spanning days like 11:00 PM to 1:00 AM
--,user or guest information too
,CONSTRAINT FK_MeetingDates_Schedule FOREIGN KEY (MeetingID)
REFERENCES Schedule(ID)
)

Answer 2

Use an existing standard. That standard is iCalendar RRules and ExDates.
Just store the recurrance rule in the db as a varchar
Use an existing library (C#) to calculate upcoming dates

Answer 3

Even though you have daily, weekly, monthly etc... still means that a meeting will occur on some specific day ... right ?
Thus
CREATE TABLE schedule
(
ID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
StartDate DATETIME NOT NULL,
EndDate DATETIME NOT NULL,
RepeatTypeID INT NOT NULL, // Daily, Weekly, Monthly, None
RepeatCount INT NOT NULL,
DayOn INT NOT NULL, // can be a calculated field based on start date using DAY function
)
I believe this can capture all your schedule options.