for a multi tenant app, we have the following database design:
which is based on shared database approach. Since we are identifying the tenants using company id (each company has a different set of employees and their tasks and so on), my question is
Do we need a companyId key in the Task table also so that every record
of task can be clearly identified using the companyId OR we should
always use a Join?
because if we use the companyId in Task that would not be a properly normalized database as the Task is would relate to a company and an employee which is also related to the company.
It is a matter of opinion. My take is to make companyId as a part of primary key and hence a mandatory field in every table.
In a multi tenant application, we should ensure that data does not get added in the table without a company code. Without making it a part of primary key or a non null field, it is upto program logic to ensure that. In my opinion, DB should also ensure that. Second issue is with the table task id. It is possible for 2 companies to have same employee id's and same task ids. DB should not restrict that.
Related
I am attempting to create an Employee table in SQL Server 2016 and I want to use EmpID as the Primary Key and Identity. Here is what I believe to be true and my question: When I create the Employee table with EmpID as the Primary Key and an Identity(100, 1) column, each time I add a new employee, SQL Server will auto create the EmpID starting with 100 and increment by 1 with each new employee. What happens if I want to import a list of existing employees from another company and those employees already have an existing EmpID? I haven't been able to figure out how I would import those employees with the existing EmpID. If there is a way to import the employee list with the existing EmpID, will SQL Server check to make sure the EmpID's from the new list does not exist for a current employee? Or is there some code I need to write in order to make that happen?
Thanks!
You are right about primary keys, but about importing employees from another company and Merging it with your employee list, you have to ask these things:
WHY? Sure there are ways to solve this problem, but why will you merge other company employees into your company employee?
Other company ID structure: Most of the time, companies have different ID structure, some have 4 characters others have only numbers so on and so forth. But you have to know the differences of the companies ID Structure.
If the merging can't be avoided, then you have to tell the higher ups about the concern, and you have to tell them that you have to give the merging company new employee ID's which is a must. With this in my, simply appending your database with the new data is the solution.
This is an extremely normal data warehousing issue where a table has data sources from multiple places. Also comes up in migration, acquisitions, etc.
There is no way to keep the existing IDs as a primary key if there are multiple people with the same ID.
In the data warehouse world we would always create a new surrogate key, which is the primary key to the table, and include the original key and a source system identifier as two attributes.
In your scenario you will probably keep the existing keys for the original company, and create new IDs for the new employees, and save the oldID in an additional column for historical use.
Either of these choices also means that as you migrate other associated data such as leave information imported from the old system, you can translate it to the new key by looking up OldID in the employee table, and finding the associated newID to associate it with when saving your lave records in the new system.
At the end of the day there is no alternative to this, as you simply cant have two employees with the same primary key.
I have never seen any company that migrate employees from another company and keep their existed employee id. Usually, they'll give them a new ID and keep the old one in the employee file for references uses. But they never uses the old one as an active ID ever.
Large companies usually uses serial of special identities that are already defined in the system to distinguish employees based on field, specialty..etc.
Most companies they don't do the same as large ones, but instead, they stick with one identifier, and uses dimensions as an identity. These dimensions specify areas of work for employees, projects, vendors ..etc. So, they're used in the system globally, and affected on company financial reports (which is the main point of using it).
So, what you need to do is to see the company ID sequence requirements, then, play your part on that. As depending on IDENTITY alone won't be enough for most companies. If you see that you can depend on identity alone, then use it, if not, then see if you can use dimensions as an identity (you could create five dimensions - Company, Project, Department, Area, Cost Center - it will be enough for any company).
if you used identity alone, and want to migrate, then in your insert statement do :
SET IDENTITY_INSERT tableName ON
INSRT INTO tableName (columns)
...
this will allow you to insert inside identity column, however, doing this might require you to reset the identity to a new value, to avoid having issues. read DBCC CHECKIDENT
If you end up using dimensions, you could make the dimension and ID both primary keys, which will make sure that both are unique in the table (treated as one set).
I'm creating a rather large APEX application which allows managers to go in and record statistics for associates in the company. Currently we have a database in oracle with data from AD which hold all the associates information. Name, Manager, Employee ID, etc.
Now I'm responsible for creating and modeling a table that will house all their stats for each employee. The table I have created has over 90+ columns in it. Some contain data such as:
Documents Processed
Calls Received
Amount of Doc 1 Processed
Amount of Doc 2 Processed
and the list goes on for well over 90 attributes. So here is my question:
When creating this table in my application with so many different columns how would I go about choosing a primary key that's appropriate? Should I link it to our employee table using the employees identification which is unique (each have a associate number)?
Secondly, how can I create these tables (and possibly form) to allow me to associate the statistic I am entering for an individual to the actual individual?
I have ordered two books from amazon on data modeling since I am new to APEX and DBA design. Not a fresh chicken, but new enough to need some guidance. An additional problem I am running into is that each form can have only 60 fields to it. So I had thought about creating tables for different functions out of my 90+ I have.
Thanks
4.2 allows for 200 items per page.
oracle apex component limits
A couple of questions come to mind:
Are you sure that the employee Ids are not recyclable? If these ids are unique and not recycled.. you've found yourself a good primary key.
What do you plan on doing when you decide to add a new metric? Seems like you might have to add a new column to your rather large and likely not normalized table.
I'd recommend a vertical table for your metrics.. you can use oracle's pivot function to make your data appear more like a horizontal table.
If you went this route you would store your employee Id in one column, your metric key in another, and value...
I'd recommend that you create a metric table consisting of a primary key, a metric label, an active indicator, creation timestamp, creation user id, modified timestamp, modified user id.
This metric table will allow you to add new metrics, change the name of the metric, deactivate a metric, and determine who changed what and when.
This would be a much more flexible approach in my opinion. You may also want to think about audit logs.
I am trying to figure out the best way to set up my Entity Diagram. I will explain based on the image below.
tblParentCustomer: This table stores information for our Primary Customers, which can either be a Business or Consumer.(They are identified using a lookup table tblCustomerType.)
tblChildCustomer: This table stores customers that are under the Primary Customer. The Primary Business customers can have Authorized Employees and Authorized Reps. The Primary Consumer customers can have Authorized Users. (They are identified using a lookup table tblCustomerType.)
tblChildAccountNumber: This table stores AccountNumbers for tblChildCustomer. These account numbers are mainly for the Child Business Customers. I may be adding Account Numbers for the Child Consumer customers, I am not sure yet, but I believe this design will allow for that if/when necessary.
Going back to tblParentCustomer : If this customer is a Consumer, I will need to add account numbers for them. My question is, do I create a 1 - Many relationship between tblParentCustomer and tblParentAccountNumber? This option would give me 2 different Account Number Tables.
Or would it make sense to create a Junction Account Table that intersects tblParentCustomer and tblChildCustomer?
The first option doesn't really make sense to me because what if there is only 1 Account number for a customer but multiple childCustomers?
Does it make sense to have 2 similar Account Tables that serve a different purpose?
Creating a many-to-many the way you want it to be, you need a link table that will make the whole thing go from 1-* and then *-1
That link table will have two FK, one linking to the parentTable and one linking to the childTable. Combination of those two FK will give you a composite PK (this is important to avoid duplicates). It will allow for any customer to be part of as many accounts as possible (duh.. it'll make the parent/child table a many-to-many relationship).
This approach is extremely common with regards to CRM or any Accounts containing people. Bring it one step further and in that table, you might want to add a "is primary contact" in the AccountMembers table. Drop the childAccountNumber table; you don't need it.
I'm working on some asp.net application, I got stuck in following business.
Suppose we have a person, and he can open both types of accounts and each account has some transaction history. Person table has some primary key say PPK, and customer table has some PK as PIN.
My question is how to solve/present this scenario in database, relation of person table to customer table is 1:2 as no person can have more than two account. and what about that transaction table? that holds all transaction history for some specific account? shall I make two transaction table (which is really a bad idea because as account type exceeds transaction tables exceeds).
Can I build their relation as 1:* (then I may need another table for that. it holds Fk of both table. )
or Can make pin as unique key and always open database for like checking limit of accounts (i.e. two).
I really need some suggestions.
All suggestions are welcome.
Thanks!
P.S: If you dont understand the question please ask me before reporting it away please!
You can either do something like this:
Or something like this:
The first model allows adding more accounts by just changing the CHECK (in case requirements change in the future), while the second would require adding another column in such case.
NOTE: The above assumes both account types are structurally identical, so they "fit" into same table. If that's not the case, you can use inheritance.
Ok you have a person table and an account table with a foreign key relationship between the two which is 1 person to many accounts. Then you have a transaction table that is related to the account id in the account table which is also 1 account to many transacations.
Now to enforce the limit of only two accounts being allowed, for that you want a trigger that checks when a record is being inserted or updated to amek sure the person currently has no more than one other record.
Is it better to create tables that store a lot of data that are related to an entity (User for example) or many tables to store said data?
For example:
User Table
Name
Email
Subscription Id
Email Notifications
Permissions
Or
User Table
Name
Email
Subscription Table
User ID
Subscription ID
Notification Table
User ID
Receives?
... etc
Please consider code in this as well, or I would have posted to ServerVault.
From a relational design standpoint what is important is the normal form you're aiming for. In general, if the "column" would require multiple values (subscription_id1, subscription_id2, etc) then it is a repeating group, and that would indicate to you that it needs to be moved to a related table. You've provided very general table and column notes, but taking a cue from the fact that you named "Email Notifications" and "Permissions" with plurals, I'm going to assume that those require related tables.