As a general question which would really help me "connect the dots" with my studies.
I am currently doing exercises working with DAO and Learning how to add tables automatically. Although i have been working with databases for many years, i question, what type of scenerarios would it be vantagious to use this function. When is it necessary to add tables to a database in an automatic way? Up until now, in all my experiences the tables i need have Always been defined from the beginning and I cant think of a situation where I could of benefited from using this function. For example, i use frequently delete queries to help me clear tables and re-populate them, but when would it be necessary to actually "create" a new table"?
Yes, I have seen a scenario where new tables were created 'on the fly' (either via SQL create, or just DAO). With a shared database on a server, the application called for importing Excel data that a particular user was responsible for, so a table was created on the fly. Multiple users, changes in staff, need to keep data independent, etc. we could create their own table (name based on userid) that they had interfaces to do whatever they wanted with their own data. Not a typical scenario, but worked well for this application.
Related
We're building a new piece of software for our company, where we want to manage our inventory.
The goal for the tool is to be customizable by the customer.
My part is mostly on the DB side. We have chosen MariaDB as our DB engine, and while we are working with the rather static functionality of a relational DB, we want to realize a rather dynamic solution.
Our chief programmer has explained to me the basics of the concept I shall implement into our DB:
We want a table which basically just consists of other tables.
Lets call it "maintable".
Maintable shall then reference its "attributes", which are the other tables.
For example, maintable references "Workstations".
"Workstations" then contains attributes like CPU, RAM, Drives, PSU etc..
And now comes the part which I didn't completely understand. The actual VALUES to these attributes in "Workstations" shall not be inserted into "Workstations". Instead, they are packed into another (junction?) table.
The reason for this approach is that the customer shall be able to customize the DB to his needs.
When the customer wants to add another attribute, he shall be able to do so. For example, if a new PSU now requires another attribute for an additional serial number, then the customer shall be able to simply create this new attribute in the front-end input form and then persist it to the DB.
If someone could point to good tutorials explaining this type of DB concept, then I would be glad as well! :=)
I am making a web application where users get and manage data from multiple tables as well as create other users to access said data. currently I have it set up for one group of users.
My question is would it be better to have multiple databases in which each database has its own user which is stored in a master table("I don't like the sound of this one") or have a column in each table defining the user group that has access to it? Are either of these a good idea or is something else more appropriate?
You should have a column in each table. In my opinion, its the correct thing to do, and also you have only one database to do mantainance.
Just imagine the time it would take to add a column to a table in the future, and you should do it in multiple databases.
I’m currently developing an Application for Win, Linux Mac. The Purpose of the Application is that multiple users are able create Projects based on a single Article. Every Article has up to 15 different Fields/Options (could also be more in future). The Fields of the Article should be changeable so I should be able to add, edit or remove them.
Fields I want to store:
Numbers
Texts (mostly options [1 Word], sometimes Comments [some sentences])
Path/Links to Files
What I want to do with the dB:
load all projects of a user at login
add, edit, remove, delete single projects
set a lock on projects (because multiple people are operating one user-account at the same time and therefore they may not be allowed to edit a project at the same time so if one starts editing it should be locked until he's saving, channelling or time-out)
What is the best way to manage this kind of Data?
Should I create a Table for each user and only make a ID Column and one where all the Values of the all the fields (who are merged to one big string)?
Should I create Tables for every Project and make Columns for every Field/Option and also one for the user / owner?
Or are there any other possibility’s?
If you don't know what you are going to store, then I doubt whether a relational database is the best option for you. Maybe a document store/noSQL database is a better decision, because you can just store documents (usually in the form of Json objects) that can have all kinds of additional fields.
A couple of such databases to look at are MongoDB, Cassandra, ElasticSearch, but you can find a big list on Wikipedia.
Within my database i have 3 different tables for different members. When saving the members details i use a form to save the members all to the same table but i would like to save them to a specific table depending on their details. for example if a member has registered with their school email i would like them to be saved within the student table, if they have used a freemail email address to be saved in the freemail table etc
Would this be run as a query or sorting the one table using if statements?
You probably should not have three tables, just a field that defines the member type. You may wish to read Fundamentals of Relational Database Design.
If you really insist on having three tables, even though it is likely to cause ever more tangled scenarios, you will either have to use VBA to gather the data from an unbound form and then fill it into the appropriate table, or ask the user which table they wish to update before you start and set up the form for that table.
It depends on your development environment. You can either change the switch to an If clause at business level or you can implement it as a database procedure. It's up to you.
http://msdn.microsoft.com/en-us/library/aa933214(v=sql.80).aspx explains how to use If clause in database
I'm working with a third party software package that is on it's own database. We are using it for the user management back bone on our application. We have an API to retrieve data and access info.
Due to the nature of information changing daily, we can only use the user_id as a pseudo FK in our application, not storing info like their username or name. The user information can change (like person name...don't ask).
What I need to do is sort and filter (paging results) one of my queries by the person's name, not the user_id we have. I'm able to get an array of the user info before hand. Would my best bet be creating a temporary table that adds an additional field, and then sorts by that?
Using MySQL for the database.
You could adapt the stored procedure on this page here to suit your needs the stored procedure is a multi purpose one and is very dynamic, but you could alter it to suit your needs for filtering the person table.
http://weblogs.asp.net/pwilson/archive/2003/10/10/31456.aspx
You could combine the data into an array of objects, then sort the array.
Yes, but you should consider specifically where you will make the temporary table. If you do it in your web application then your web server is stuck allocating memory for your entire table, which may be horrible for performance. On the other hand, it may be easier to just load all your objects and sort them as suggested by eschneider.
If you have the user_id as a parameter, you can create a user defined function which retrieves the username for you within the stored procedure.
Database is on different servers. For all purposes, we access it via an API and the data is then turned into an array.
For now, I've implemented the solution using LINQ to filter and out the array of objects.
Thanks for the tips and helping me go in the right direction.