I want to make a site in which every user has his own customers and products to manage.
Whats the best way to handle this??
Is it OK to use an additional field for each entry specifying the user this entry belongs to ? or there is a better way?
Im using sql server if it matters.
Thank You.
not really much info in the question... however:
it is much simpler to scale some more data in a single database than to create additional databases. so YES - make one database.
the exact schema you choose is more subtle - normalize, and link rows to appropriate users
Do NOT I repeat do NOT create a database per user, not even a table per user.
Add a column UserID to any table that may need to reference a person with a product or order.
Related
i wanted to create via Excel or Oracle a database for a Storage room that is filled with all kinds of Computer parts and stuff.
I never created something like that, so i wanted to know if you could help me out giving me an advice how to create a database for a beginner
It should be possible to insert and remove parts or even update them
Hope my question is readable and understandable.
Thanks
A simple option to do that - not only the table so that you could write your own DML statements (to insert, update or delete rows) - but to create a nice application - is to use Oracle Application Express (Apex).
Depending on database version you use, it might already be installed by default. If not, ask your DBA to install it.
Alternatively, create a free account on apex.oracle.com; you'll get limited space (more than enough to do what you want to do).
In Application Builder, use the Excel file you have as a "source" which will then be used by Apex's wizard to create a table in the database, as well as application, true GUI which works and looks just fine.
If you don't have anything at all, not even an Excel file, well ... that's another problem and requires some more work to be done.
you have to know what you want (OK, a storage room)
is a single table enough to contain all information you'd want to collect?
if so, which columns (attributes) do you want to collect?
if not (for example, you'd want to "group" items), you'd need at least two tables which will be related to each other by the means of master-detail relationship, which also means that you'll have to create a foreign key constraint
which datatypes are appropriate for certain attributes? You wouldn't store item names into number datatype, right? Nor should you put dates (when item entered the storage room) as a string in varchar2 column, but into a date datatype column
etc.
Basically, YMMV.
My application has a database table that is used to record the attendance of employees. And the column attedance_status has only three possible values - "present", "absent", "on_leave", and NULL as default.
How do I add it to the database? So far I have come up with two possible ways.
Create another table attendance_status with status_id and status_value and add the above values to it. And then use the id in the application for all SQL queries.
Probably the bad way. Hardcode the values (maybe in a config file) and use it throughout the app's SQL queries.
Am I missing the right way? How should this be approached?
Either will work, but Option 1 will give you flexibility in the event that the requirements change and is the standard data model. I would, however, name my columns a little differently. I would have id, value, name. Then the references become attendance_status.id and attendance_status.value. The third column is available for use in displays or reports or whatever. value is on_leave and name is On leave.
Option 2 works provided the data input point is totally closed. If someone codes new functionality there is the risk that he or she will invent something different to mean the same thing like onLeave.
The setup
I have the following database setup:
CentralDB
Table: Stores
Table: Users
Store1DB
Table: Orders
Store2DB
Table: Orders
Store3DB
Table: Orders
Store4DB
Table: Orders
... etc
CentralDB contains the users, logging and a Stores table with the name of each store database and general information about each store such as address, name, description, image, etc...
All the StoreDB's use the same structure just different data.
It is important to know that the list of stores will shrink and increase in the future.
The main client communicating with this setup is an API REST Service which gets passed a STOREID in the Header of each request telling it which database to connect to. This works flawlessly so far.
The reasoning
Whenever we need to do database maintenance on one store, we don't want all other stores to be down.
Backup management should be per store
Not having to write the WHERE storeID=x every time and for every table
Performance: each store could run on its own database server if the need arises
The goal
I need my REST API Service to somehow get all orders from all stores in one query.
Will you help me figure out a way to do this without hardcoding all storedb names? I was thinking about a stored procedure on the CentralDB but I was hoping there would be other solutions. In any case it has to be very efficient.
One option would be to have a list of databases stored in a "system" table in CentralDB.
Then you could create a stored procedure that would read the database names from the table, loop through them with cursor and generate a dynamic SQL that would UNION the results from all the databases. This way you would get a single recordset of results.
However, this database design is IMHO flawed. There is no reason for using multiple databases to store data that belongs to the same "domain". All the reasons that you have mentioned can be solved by using a single database with proper database design. Having multiple databases will create multiple problems on the long term:
you will need to change structure of all the DBs when you modify your database model
you will need to create/drop new databases when new stores are added/removed from your system
you will need to have items and other entities that are "common" to all the stores duplicated in all the DBs
what about reporting requirements (e.g. get sales data for stores 1 and 2 together, etc.) - this will require creating complex union queries...
etc...
On the long term, managing and maintaining this model will be a big pain.
I'd maintain a set of views that UNION ALL all the data. Every time a store is added or deleted those views must be updated. This can be automated.
The views provide an illusion to the application that there is only one database.
What I would not do is have each SQL query or procedure query all the database names and create dynamic SQL. That would entail lots of code duplication and an unnecessary loss of performance. This approach is error prone. Better generate code once in a central place and have all other SQL code reference that generated code.
here is something interesting that I have been asked. It has to do with the encryption of data in a non encrypted database.
The story has as follows. We have a database, not encrypted and also none column encrypted in any of its tables. Now, we'd like to control the trafic of the data depending on who is asking for this. Let me explain more clear:
We have a table with the name: table1
This table has one column with the name: SName
We'd like to reach the following result. A user connected to the SQL Server Management Studio if runs the following query:
select * from table1
to take no result or if he/she takes a result, this result to be scrambled.
Now from inside the application the table should exchange data from/to the application in the normal mode.
Do you know if there is a setting, or an implementation or an external tool that can provide this functionality?
I think that this is quite interesting case!
Thank you.
Use permissions to stop that person reading the table at all.
Or use a VIEW to hide the table and have a WHERE clause in that that applies a filter silently: this could refer to another table with a list of approved users.
This isn't really an encryption (well, obfuscation in this case) issue.
I need to store data's change histories in database. For example some time some user modify some property of some data. The expected result is we can get the change histories for one data like
Tom changed title to 'Title one;'
James changed name to 'New name'
Steve added new_tag 'tag23'
Based on these change histories we can get all versions for some data.
Any good idea to achieve this? Not limited to traditional relation database.
These are commonly called audit tables. How I generally manage this is using triggers on the database. For every insert/update from a source table the trigger copies the data into another table called the same table name with an _AUDIT appended to it (the naming convention does not matter, it's just what I use). ORACLE provides you with something called journal tables. Using ORACLE designer (or manually) you can achieve the same thing and often developers put a _JN to the end of the journal/audit table. This, however, works the same, with triggers on the source table copying data into the audit table.
EDIT:
I should also note that you can create a new separate schema to manage just your audit tables or you can keep them in your schema with the source tables. I do both, it just depends on the situation.
I wrote an article about various options: http://blog.schauderhaft.de/2009/11/29/versioned-data/
If you are not tied to a relational database, there are things called 'append only' databases (I think), which never change data, but only append new versions. For your case this sounds kind of perfect. Unfortunately I don't know of any implementation.