So I have this application that I'm drawing up and I start to think about my users. Well, My initial thought was to create a table for each group type. I've been thinking this over though and I'm not sure that this is the best way.
Example:
// Users
Users [id, name, email, age, etc]
// User Groups
Player [id, years playing, etc]
Ref [id, certified, etc]
Manufacturer Rep [id, years employed, etc]
So everyone would be making an account, but each user would have a different group. They can also be in multiple different groups. Each group has it's own list of different columns. So what is the best way to do this? Lets say I have 5 groups. Do I need 8 tables + a relational table connecting each one to the user table?
I just want to be sure that this is the best way to organize it before I build it.
Edit:
A player would have columns regarding the gear that they use to play, the teams they've played with, events they've gone to.
A ref would have info regarding the certifications they have and the events they've reffed.
Manufacturer reps would have info regarding their position within the company they rep.
A parent would have information regarding how long they've been involved with the sport, perhaps relations with the users they are parent of.
Just as an example.
Edit 2:
**Player Table
id
user id
started date
stopped date
rank
**Ref Table
id
user id
started date
stopped date
is certified
certified by
verified
**Photographer / Videographer / News Reporter Table
id
user id
started date
stopped date
worked under name
website / channel link
about
verified
**Tournament / Big Game Rep Table
id
user id
started date
stopped date
position
tourney id
verified
**Store / Field / Manufacturer Rep Table
id
user id
started date
stopped date
position
store / field / man. id
verified
This is what I planned out so far. I'm still new to this so I could be doing it completely wrong. And it's only five groups. It was more until I condensed it some.
Although I find it weird having so many entities which are different from each other, but I will ignore this and get to the question.
It depends on the group criteria you need, in the case you described where each group has its own columns and information I guess your design is a good one, especially if you need the information in a readable form in the database. If you need all groups in a single table you will have to save the group relevant information in a kind of object, either a blob, XML string or any other form, but then you will lose the ability to filter on these criteria using the database.
In a relational Database I would do it using the design you described.
The design of your tables greatly depends on the requirements of your software.
E.g. your description of users led me in a wrong direction, I was at first thinking about a "normal" user of a software. Basically name, login-information and stuff like that. This I would never split over different tables as it really makes tasks like login, session handling, ... really complicated.
Another point which surprised me, was that you want to store the equipment in columns of those user's tables. Usually the relationship between a person and his equipment is not 1 to 1 and in most cases the amount of different equipment varies. Thus you usually have a relationship between users and their equipment (1:n). Thus you would design an equipment table and there refer to the owner's user id.
But after you have an idea of which data you have in your application and which relationships exist between your data, the design of the tables and so on is rather straitforward.
The good news is, that your data model and database design will develop over time. Try to start with a basic model, covering the majority of your use cases. Then slowly add more use cases / aspects.
As long as you are in the stage of planning and early implementation phasis, it is rather easy to change your database design.
Related
I know there is a lot of posts out there discussing Db design for a chat system, but they didn't explain anything about the scalability of that design, so here my question.
I want to design a Db of a real-time chat between 2 or more users, let's take 2 users first, here what I came up with.
Table 1:
name: User
fields: id, name
Table 2
name: Chat Room
fields: id, user1, user2
Table 3:
name: Message
fields: Chat_room_id, user_id, message
Now considering Facebook in mind, it has around 2 billion active users per month and let say 1 billion of them indulge in chatting and each user sends 100 messages.
which make 100 Billion entries in table: Message, so the question is,
"Will Mysql or Postgres be able to handle this much of entries and show particular chat room messages in real-time ?" if not then what should be the best practice to follow that, I know that it also depends on the server on which RDBMS is installed but still want to know the optimum architecture.
PS: I am using Django as backend and AngularJs for asynchronous behavior
100 Billions rows in one table will never work online. Not only all possible partitioning ways are applied to reduce the sizes, but also separation of active/passive data strategies. But nevertheless all the high maters, the answer:
Postgres is indeed effective working with big data itself.
and yet:
Postgres has not effective enough strategy to fight poor design
Look at your example: table chat_room lists two users in separate columns - what for? You have user_id in messages referencing users.id. And you have chat_room.id in it, so you have data which users were in that chat_room. Now if your idea was to pre-aggregate which users participated in chat_room over time or at all, make it one array column, like (chat_room.id int, users_id bigint[]) or if you want join time and leave time, add corresponding attributes. active/passive data can be implemented using archived chat_rooms in different relation then active ones. Btw aggregation on who participated in that chatroom can be performed on such archiving...
Above is not instructions for action, just expression. There is no best practice for database schema. First make a clear plan what your chat will do, then make db schema, try it, improve, try, improve, try, improve and so on, until everything works. If you have concerns on how it will work with 100 billions of rows - fill it up and check...
We presently use a pen/paper based roster to manage table games staff at the casino. Each row is an employee, each column is a 20 minute block of time and each cell represents what table the employee is assigned to, or alternatively they've been assigned to a break. The start and end time of shifts for employees vary as do the games/skills they can deal. We need to keep a copy of the rosters for 7 years, with paper this is fairly easy, I'm wanting to develop a digital application and am having difficulty how to store the data in a database for archiving.
I'm fairly new to working with databases, I think I understand how to model the data for a graph database like neo4j, but I had difficulty when it came to working with time. I've tried to learn about RDBMS databases like MySQL, below is how I think the data should be modelled. Please point out if I'm going in the wrong direction or if a different database type would be more appropriate, it would be greatly appreciated!
Basic Data
Here is some basic data to work with before we factor in scheduling/time.
Employee
- ID Number
- Name
- Skills (Blackjack, Baccarat, Roulette, etc)
Table
- ID Number
- Skill/Type (Can only be one skill)
It may be better to store the roster data as a file like JSON instead? Time sensitive data wouldn't be so much of a problem then. The benefit of going digital with a database would be queries, these could help assist time consuming tasks where human error is common.
Possible Queries
Note: Staff that are on shift are either on a break or on the floor (assigned to a table), Skills have a major or minor type based on difficulty to learn.
What staff have been on the floor for 80 minutes or more? (They are due for a break)
What open tables can I assign this employee to based on their skillset?
I need an employee that has Baccarat skill but is not already been assigned to a Baccarat table.
What employee(s) was on this table during this period of time?
Where was this employee at this point in time?
Who is on shift right now?
How many staff on shift can deal Blackjack?
How many staff have 3 major skills?
What staff have had the Baccarat skill for at least 3 months?
These queries could also be sorted by alphabetical order or time, skill etc.
I'm pretty sure I know how to perform these queries with cypher for neo4j provided I model the data right. I'm not as knowledgeable with SQL queries, I've read it can get a bit complicated depending on the query and structure.
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MYSQL Specific
An employee table could contain properties such as their ID number and Name, but am I right that for their skills and shifts these would be separate tables that reference the employee by a unique integer(I think this is called a foreign key?).
Another table could store the gaming Tables, these would have their own ID and reference a skill/gametype with a foreign key.
To record data like the pen/paper roster, each day could have a table with columns starting from 0000 increasing by 20 in value going all the way to 2340? Prior to the time columns I could have one for staff where each employee is represented with their foreign key, the time columns would then have foreign keys to the assigned gaming Tables, the row data is bound to have many cells that aren't populated since the employee shift won't be 24/7. If I'm using foreign keys to reference gaming Tables I now have a problem when the employee is on break? Unless I treat say the first gaming Table entry as a break?
I may need to further complicate things though, management will over time try different gaming Table layouts, some of the gaming Tables can be converted from say Blackjack to Baccarat. this is bound to happen quite a bit over 7 years, would I want to be creating new gaming Table entries or add a column to use a foreign key and refer to a new table that stores the history of game types during periods of time? Employees will also learn to deal new games during their career, very rarely they may also have the skill removed.
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Neo4j Specific
With this data would I have an Employee and a Table node that have "isA" relationship edges mapping to actual employees or tables?
I imagine with the skills for the two types I would be best with a Skill node and establish relationships like so?: Blackjack->isA->Skill, Employee->hasSkill->Blackjack, Table->typeIs->Blackjack?
TIME
I find difficulty when I want this database to now work with a timeline. I've come across the following suggestions for connecting nodes with time:
Unix Epoch seems to be a common recommendation?
Connecting nodes to a year/month/day graph?
Lucene timeline? (I don't know much about this or how to work with it, have seen some mention it)
And some cases with how time and data relate:
Staff have varied days and start/end times from week to week, this could be shift node with properties {shiftStart,shiftEnd,actualStart,actualEnd}, staff may arrive late or get sick during shift. Would this be the right way to link each shift to an employee? Employee(node)->Shifts(groupNode)->Shift(node)
Tables and Staff may have skill data modified, with archived data this could be an issue, I think the solution is to have time property on the relationship to the skill?
We open and close tables throughout the day, each table has open/close times for each day, this could change in a month depending on what management wants, in addition the times are not strict, for various reasons a manager may open or close tables during the shift. The open/closed status of a table node may only be relevant for queries during the shift, which confuses me as I'd want this for queries but for archiving with time it might not make sense?
It's with queries that I have trouble deciding when to use a node or add a property to a node. For an Employee they have a name and ID number, if I wanted to find an employee by their ID number would it be better to have that as a node of it's own? It would be more direct right, instead of going through all employees for that unique ID number.
I've also come across labels just recently, I can understand that those would be useful for typing employee and table nodes rather than grouping them under a node. With the shifts for an employee I think should continue to be grouped with a shifts node, If I were to do cypher queries for employees working shifts through a time period a label might be appropriate, however should it be applied to individual shift nodes or the shifts group node that links back to the employee? I might need to add a property to individual shift nodes or the relationship to the shifts group node? I'm not sure if there should be a shifts group node, I'm assuming that reducing the edges connecting to the employee node would be optimal for queries.
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If there are any great resources I can learn about database development that'd be great, there is so much information and options out there it's difficult to know what to begin with. Thanks for your time :)
Thanks for spending the time to put a quality question together. Your requirements are great and your specifications of your system are very detailed. I was able to translate your specs into a graph data model for Neo4j. See below.
Above you'll see a fairly explanatory graph data model. In case you are unfamiliar with this, I suggest reading Graph Databases: http://graphdatabases.com/ -- This website you can get a free digital PDF copy of the book but in case you want to buy a hard copy you can find it on Amazon.
Let's break down the graph model in the image. At the top you'll see a time indexing structure that is (Year)->(Month)->(Day)->(Hour), which I have abbreviated as Y M D H. The ellipses indicate that the graph is continuing, but for the sake of space on the screen I've only showed a sub-graph.
This time index gives you a way to generate time series or ask certain questions on your data model that are time specific. Very useful.
The bottom portion of the image contains your enterprise data model for your casino. The nodes represent your business objects:
Game
Table
Employee
Skill
What's great about graph databases is that you can look at this image and semantically understand the language of your question by jumping from one node to another by their relationships.
Here is a Cypher query you can use to ask your questions about the data model. You can just tweak it slightly to match your questions.
MATCH (employee:Employee)-[:HAS_SKILL]->(skill:Skill),
(employee)<-[:DEALS]-(game:Game)-[:LOCATION]->(table:Table),
(game)-[:BEGINS]->(hour:H)<-[*]-(day:D)<-[*]-(month:M)<-[*]-(year:Y)
WHERE skill.type = "Blackjack" AND
day.day = 17 AND
month.month = 1 AND
year.year = 2014
RETURN employee, skill, game, table
The above query finds the sub-graph for all employees who have the skill Blackjack and their table and location on a specific date (1/17/14).
To do this in SQL would be very difficult. The next thing you need to think about is importing your data into a Neo4j database. If you're curious on how to do that please look at other questions here on SO and if you need more help, feel free to post another question or reach out to me on Twitter #kennybastani.
Cheers,
Kenny
I am trying to figure out how I should go about building my database structure (tables) for user information on my website. The kinds of information that I will be storing (at this time anyways) are:
About Me
Birthday (January, 1, 1970)
Sex (Male/Female)
Interested In: (Male, Female, Both)
Relationship Status: (Single, In a Relationship, Engaged, Married)
Website: (mywebsite.com)
From: (Cupertino, California)
So this is the type of information I will be storing for now. My question basically is, should I have this be one table only? Or would it be better to split the information up depending on what it was (my users have a unique ID which would go along with each table of information, obviously). So I'm not sure if I should have a table exclusively for Birthdays with the columns: userID, Month, Day, Year; or what.
If a user only needs to store one piece of information for an attribute, then you don't need a separate table for it. For example, a user only has one birthday. The only reason you would need a separate Birthdays table would be if you want to store multiple birthdays for the same userid. Each one of the attributes you've listed look like they'd be fine in one Users table.
As for splitting up Birthdays into the columns: userID, Month, Day, Year, it all depends on how you're going to use that information. Will you ever need to know just the Month, Day, or Year that a user's birthday falls on? If that's a common need, you might want to store them separately. It's usually not, so you probably just want to store it as a single Date value.
Note: You can take a look at the schema used by Stack Overflow by checking out the Data Explorer. They keep a similar collection of data in one Users table.
In the vast majority of cases, I've seen what you're asking being stored in one table - usually user or users.
Perhaps including a number of other elements too:
user id (unique)
registration date
status (live/expired/banned)
user hash
plus a variety of others...
Honestly - It's dependent on what you're building and how it's built, but my advice would be to start simple.
On your point about birthdays, just store the date in mysql date format:
YYYY-MM-DD
That way, you can manipulate it in a variety of ways using mysql functions.
Hope this helps.
I'm working on a web application where I need to do some research before I implement the database. I hope you can help me make some good decisions before I start to code.
Today i have a database that among other things contains about two million contacts in a table
Contact:
cid, name, phone, address, etc...
Users of the application can search the contact table based on different criteria, and get a list of contacts.
Users are stored i a separate database table
User: uid, name, email, etc...
Now I want to make the users able to store a search result as a selection. The selection has to be a list of cid's representing every contact in the search result the user got. When the selection is stored, a user can open the selection and add notes, statuses etc to the different contacts in the selection.
My first thought is to make a selection table and a selection-contact mapping table like this:
Selection: sid, name, description, uid, etc
SelectionContactMap: sid, cid, status, note, etc...
With an average selection size between 1 000 and 100 000 contacts, and several thousand users storing many selections, I see that the SelectionContactMap table is going to grow very big very fast.
The database is MySql and the application is written in PHP. I'm on a limited budget so I can not throw unlimited hardware on the task.
I'm I on the wrong way here?
Do you have any suggestions to solve this the best possible way?
Other database?
MySql specific suggestions, table type etc?
Other database design?
Any comments and suggestions are appreciated.
Thanks in advance :)
-- Tor Inge
Question: What happens if the results of the query change - eg: a selected contact no longer has the chosen attribute or a new contact gets added?
If the answer is "The result set should be updated" - then you want to store the criteria in the database, not the results themselves.
If you need to cache the results for a period of time, this may be better handled by the application, not the database.
I have an Access application, in which I have an employee table. The employees are part of several different levels in the organization. The orgranization has 1 GM, 5 department heads, and under each department head are several supervisors, and under those supervisors are the workers.
Depending on the position of the employee, they will only have access to records of those under them.
I wanted to represent the organization in a table with some sort of level system. The problem I saw with that was that there are many ppl on the same level (for example supervisors) but they shouldn't have access to the records of a supervisor in another department. How should I approach this problem?
One common way of keeping this kind of hierarchical data in a database uses only a single table, with fields something like this:
userId (primary key)
userName
supervisorId (self-referential "foreign key", refers to another userId in this same table)
positionCode (could be simple like 1=lakey, 2=supervisor; or a foreign key pointing to another table of positions and such)
...whatever else you need to store for each employee...
Then your app uses SQL queries to figure out permissions. To figure out the employees that supervisor 'X' (whose userId is '3', for example) is allowed to see, you query for all employees where supervisorId=3.
If you want higher-up bosses to be able to see everyone underneath them, the easiest way is just to do a recursive search. I.e. query for everyone that reports to this big boss, and for each of them query who reports to them, all the way down the tree.
Does that make sense? You let the database do the work of sorting through all the users, because computers are good at that kind of thing.
I put the positionCode in this example in case you wanted some people to have different permissions... for example, you might have a code '99' for HR employees which have the right to see the list of all employees.
Maybe I'll let some other people try to explain it better...
Here's an article from Microsoft's Access Cookbook that explains these queries rather well.
And here is a somewhat chunky explanation of the same.
Here's a completely different method (the "adjacency list model") that you might find useful, and his explanation is pretty good. He also points out some difficulties with both methods (when he talks about the tables being "denormalized").