I want two different data-sources in my application (one is for testing)
How can I tell to a Model what data-source to use?
And is it also also possible to do that on the fly in a Controller?
Use ConnectionManager::alias():
http://api.cakephp.org/3.0/class-Cake.Datasource.ConnectionManager.html#_alias
Fore example this will make all tables that require the default connection to use `custom:
ConnectionManager::alias('custom', 'default');
Related
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.
I am having a main stream website and I would like to include Forum functionality. Since it is a java based system, I opt for Jforum. Now since the JForum having it's own login table and use it from there, I would like to make this to use mainstream login sysem. Can any one post me what are the best practice to do it? Duplicating the data in both the table? Create a view and refresh periodically? I am using MySQL database.
Copying the data from one table to another is not a good idea, as it can introduce inconsistencies in the data. The best solution is to create a View, as you mentioned. Simply add any columns that JForum needs to the main stream website database, and create a view that simulates the table name and column format that JForum is expecting. If done correctly, JForum should simply read from the VIEW which is nothing but a SQL query that changes your existing Users table to appear the way it's expecting it to.
I am a little new to linq-to-sql. I was just thinking suppose you wanted a subset of fields (in your db table) to actually be a data model in your application, what do you do? What I have thought of so far is to create a view from the actual db table and build linq-able classes using it.
Or is there a better way of doing this?
try these Walkthrough: Creating LINQ to SQL Classes (O/R Designer)
or these implemented in MVC Creating Model Classes with LINQ to SQL
One option is you can create Anonymous Types and use it.
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.
I am trying to inherit from my generated datacontext in LinqToSQL - something like this
public class myContext : dbDataContext {
public System.Data.Linq.Table<User>() Users {
return (from x in base.Users() where x.DeletedOn.HasValue == false select x);
}
}
But my Linq statement returns IQueryable which cannot cast to Table - does anyone know a way to limit the contents of a Linq.Table - I am trying to be certain that anywhere my Users table is accessed, it doesn't return those marked deleted. Perhaps I am going about this all wrong - any suggestions would be greatly appreciated.
Hal
Another approach would to be use views..
CREATE VIEW ActiveUsers as SELECT * FROM Users WHERE IsDeleted = 0
As far as linq to sql is concerned, that is just the same as a table. For any table that you needed the DeletedOn filtering, just create a view that uses the filter and use that in place of the table in your data context.
You could use discriminator column inheritance on the table, ie. a DeletedUsers table and ActiveUsers table where the discriminator column says which goes to which. Then in your code, just reference the Users.OfType ActiveUsers, which will never include anything deleted.
As a side note, how the heck do you do this with markdown?
Users.OfType<ActiveUsers>
I can get it in code, but not inline
Encapsulate your DataContext so that developers don't use Table in their queries. I have an 'All' property on my repositories that does a similar filtering to what you need. So then queries are like:
from item in All
where ...
select item
and all might be:
public IQueryable<T> All
{
get { return MyDataContext.GetTable<T>.Where(entity => !entity.DeletedOn.HasValue); }
}
You can use a stored procedure that returns all the mapped columns in the table for all the records that are not marked deleted, then map the LINQ to SQL class to the stored procedure's results. I think you just drag-drop the stored proc in Server Explorer on to the class in the LINQ to SQL designer.
What I did in this circumstance is I created a repository class that passes back IQueryable but basically is just
from t in _db.Table
select t;
this is usually referenced by tableRepository.GetAllXXX(); but you could have a tableRepository.GetAllNonDeletedXXX(); that puts in that preliminary where clause to take out the deleted rows. This would allow you to get back the deleted ones, the undeleted ones and all rows using different methods.
Perhaps my comment to Keven sheffield's response may shed some light on what I am trying to accomplish:
I have a similar repository for most
of my data access, but I am trying to
be able to traverse my relationships
and maintain the DeletedOn logic,
without actually calling any
additional methods. The objects are
interrogated (spelling fixed) by a StringTemplate
processor which can't call methods
(just props/fields).
I will ultimately need this DeletedOn filtering for all of the tables in my application. The inherited class solution from Scott Nichols should work (although I will need to derive a class and relationships for around 30 tables - ouch), although I need to figure out how to check for a null value in my Derived Class Discriminator Value property.
I may just end up extended all my classes specifically for the StringTemplate processing, explicitly adding properties for the relationships I need, I would just love to be able to throw StringTemplate a [user] and have it walk through everything.
There are a couple of views we use in associations and they still appear just like any other relationship. We did need to add the associations manually. The only thing I can think to suggest is to take a look at the properties and decorated attributes generated for those classes and associations.
Add a couple tables that have the same relationship and compare those to the view that isn't showing up.
Also, sometimes the refresh on the server explorer connection doesn't seem to work correctly and the entities aren't created correctly initially, unless we remove them from the designer, close the project, then reopen the project and add them again from the server explorer. This is assuming you are using Visual Studio 2008 with the linq to sql .dbml designer.
I found the problem that I had with the relationships/associations not showing in the views. It seems that you have to go through each class in the dbml and set a primary key for views as it is unable to extract that information from the schema. I am in the process of setting the primary keys now and am planning to go the view route to isolate only non-deleted items.
Thanks and I will update more later.