Imagine that I have a Table Cine. It holds name, director, etc. of movies. It can start and finish in any time, and this time is created dynamically, in another Table: Schedule.
Thus, between Cine-Schedule there is One-To-Many relation. So, this would be solved by adding Foreign Key to Schedule. Some thing like this:
Cine
ID Name
1...Matrix
Schedule
CineID. From To...... WeekDay
1.. ........17.00. 19.00..... Wednesday
1...........20.00. 22.00.....Thursday
Now imagine that another table also wants to use this Scheduling, which is conceptually totally separated from Cine, let say CarRevision.
In this case, how would be "better design" of database.
Adding another foreign ID to Schedule?
Schedule
CineID. RevisionID From To...... WeekDay
1.. .........Null.............17.00. 19.00..... Wednesday
1............Null.............20.00. 22.00..... Thursday
Null.........325............14.13. 14.34..... Monday
Creating another table, like RevisionSchedule, same with Schedule, but with -logically- different foreign ID?
Other solution? What about if we have many -conceptually- different Tables that want to use Schedule?
for proper normalization, you would remove cine_id from the schedule - since it is not directly part of the definition of a schedule
you would make a new table
cine_schedule
--------------
cine_id
schedule_id
start_date
end_date
you would also build other relationships as appropriate
car_schedule
--------------
car_id
schedule_id
etc.
Related
I have an Event table that contains the following columns:
ID
UserId
Title
StartDate
EndDate
Repeat (Check constraint (M,W,D)) -- Monthly, Weekly, Daily
Time
DaysId (FK)
Question 1
I want to add a column for storing many days of month like:
Event 1 has to be repeated monthly in Month days (2, 4, 8, 23)
is it a good idea to store them in one column separated by (, | or etc...)?
is it a good idea to store them in another table as MonthDays (ID, DayNumber)?
Or is there any other way i can accomplish such thing for a fast and efficient way.
Question 2
Events table has a FK column days. which will be not null when the Repeat column value is Weekly. I'm storing days values in another table Days which has the following columns
ID
Mon (bit)
Tue (bit)
Wed (bit)
...
Is there a better way for storing the days?
This will answer your question, but not quite as directly as you would like.
You seem to have an entity eventScheduleRule that defines one rule for an event. This could be on the 3rd of every month. Or the 4th Friday. Or the Sunday after the first full moon of the vernal equinox. Whatever rules you accept, you can have one rule that sets out one or more days for an event.
Then event would seem to contain one or more rules for scheduling the event.
I would suggest following a structure such as this for setting up the scheduling.
The first image below is my database schema for a project that will use psql, ruby and active record.
While writing my schema, things got a bit complex. My "special_days" table ended up becoming a join table for "days_of_week" and "organizations". I'm assuming that this is not best practice and will end up causing me trouble.
In the second schema below, I made a separate join table for "days of week" and "organizations". My special_days table still needs to be associated with a day_of_week and an organization, so I think I have to keep the joining information in the special_days table. Is there a better way to do this? It seems that my second attempt is too repetitive.
These are my relationships:
days of week & organizations | many to many
city & organizations | one to many
organization & special days | one to many
day of week & special days | one to many
Some more information about the requirements might be useful. Are you required to do something like define which days are holidays, which days are paydays, etc. (e.g. many organizations would define Sat and Sun as non-work days and many U.S. organization would define July 4 as a non-work day)? I'm not sure what days_of_the week represents. Is this a table with 7 records in it (M,T,W,Th,F,S,Sun)? If I'm guessing correctly at the requirements it might be better to do something like have a table called special_day that has a date column and a recurrence column (e.g. weekly, monthly, yearly, etc.). You could then have a organization_special_day table that is a many-to-many join table on organization and special_day.
I am trying to make sense of dimension modeling. While reading a dimension modeling book, I have created a star schema.
The fact table is a Accumulating snapshot table and it has multiple date columns which are linked to a date dimension using a surrogate key.
FactApplicants
{
Interview_No_Show_Date_Key (FK)
Cancel_Date_Key (FK)
Interviewed_Date_Key (FK)
. ....
Applicant_Key(FK)
InquiryCount int
}
DimDate
{
Date_Key (PK, int),
FullDateUSA (char(10))
Date (datetime)
}
I do have a well defined process for which i am trying to make this star schema for. I have a date field in the fact table for each of this step as I need to prepare funnel like report and activity reports. So the question really is
Is this correct? can a fact table refer to same date dimension table multiple times?
The examples I am seeing all over the internet seems to indicate this is correct but i am having hard time making it work with Pentaho reporting. so I am not sure if its a design problem or its something i am not doing correctly in Pentaho
Yes it is correct to refer to the date dimension multiple times
Yes, a fact can refer to the same dimension multiple times. However, given only what I see in your example, I am not sure why you need the date dimension. The date in applicants is just a date and can be used as an attribute without referring to a separate date dimension. It's just the attribute "date". You would need a separate date dimension if, for example, (1) you want to ensure that only valid dates are used, or (2) you want to elevate date to a full calendar in which other attributes are used to describe a date, such as day of the week, weekday/weekend, holiday, etc. or (3) you want to rollup date to other levels, such as week, month, year.
I am very new to Access and I am working on a database and I need help coming up with a solution:
I am recording data from a bunch of asphalt laying crews. Each crew has a record with a field for production and equipment. Each crew has varying types of equipment and varying quantities of equipment. Therefore, I would need to create a new table for the type and quantity of equipment every time I enter a new record... can someone please help me come up with a solution?
You do not need a new table for each record, you just need a properly set up table. Let us say:
Crews table
CrewID
Location
Etc
CrewMembers table
MemberID
Etc
CrewEquipment table
CrewID
EquipmentID
DateIn
DateOut
Etc
Equipment table
EquipmentID
Details
Etc
You might like to read http://r937.com/relational.html
With the above set-up, you can have a Crew form with subforms for members and equipment. You can get an idea from this create form to add records in multiple tables
Creating new table everytime is not solution, you should clear some RDBMS concept like normalization first. Create separate table for
crew member (which include crew member id, his name, salary/wages
List item per hour) equipments (which include equipments id, operation cost per hour etc)
Shift (can be separated by date and shift time etc)
Then create proper relationship between tables and this way you can create proper relational database system. so finish some basic tutorial first then start development.
I'm working on a project that must store employees' timetables. For example, one employee works Monday through Thursday from 8am to 2pm and from 4pm to 8pm. Another employee may work Tuesday through Saturday from 6am to 3pm.
I'm looking for an algorithm or a method to store these kind of data in a MySQL database. These data will be rarely accessed so it's not important performance questions.
I've thought to store it as a string but I don't know any algorithm to "encode" and "decode" this string.
As many of the comments indicate, it's usually a poor idea to encode all the data into a string that is basically meaningless to the data base. It's usually better to define the data elements and their relations and represent these structures in the data base. The Wikipedia article on data models is a good overview of what's involved (although it's way more general than what you need). The problem you are describing seems simple enough that you could do this with pencil and paper.
One way to start is to write down a lists of logical relationships between concepts in your problem. For instance, the list might look like this (your rules may be different):
Every employee follows a single schedule.
Every employee has a first and last name, as well as an employee ID. Different employees may have the same name, but each employee's ID is unique to that employee.
A schedule has a start and stop day of the week and a start and stop time of day.
The start and stop time is the same for every day of the schedule.
Several employees may be on the same schedule.
From this, you can list the nouns used in the rules. These are candidates for entities (columns) in the data base:
Employee
Employee ID
Employee first name
Employee last name
Schedule
Schedule start day
Schedule start time
Schedule end day
Schedule end time
For the rules I listed, schedules seem to exist independently of employees. Since there needs be a way of identifying which schedule an employee follows, it makes sense to add one more entity:
Schedule ID
If you then look at the verbs in the rules ("follows", "has", etc.), you start to get a handle on the relationships. I would group everything so far into two relationships:
Employees
ID
first_name
last_name
schedule_ID
Schedules
ID
start_day
start_time
end_day
end_time
That seems to be all that's needed by way of data structures. (A reasonable alternative to start_day and end_day for the Schedules table would be a boolean field for each day of the week.) The next step is to design the indexes. This is driven by the queries you expect to make. You might expect to look up the following:
What schedule is employee with ID=xyz following?
Who is at work on Mondays at noon?
What days have nobody at work?
Since employees and schedules are uniquely identified by their respective IDs, these should be the primary fields of their respective tables. You also probably want to have consistency rules for the data. (For instance, you don't want an employee on a schedule that isn't defined.) This can be handled by defining a "foreign key" relationship between the Employees.schedule_ID field and the Schedules.ID field, which means that Employees.schedule_ID should be indexed. However, since employees can share the same schedule, it should not be a unique index.
If you need to look up schedules by day of week and time of day, those might also be worth indexing. Finally, if you want to look up employees by name, those fields should perhaps be indexed as well.
Assuming you're using PHP:
Store a timetable in a php array and then use serialize function to transform it in a string;
to get back the array use unserialize.
However this form of memorization is almost never a good idea.