I'm using an Nhibernate version 3.0 and this is my first time im using it.I would like to know how can i create an hbm.xml file for the tables where relationship exists between them. Here is my scenario i have two tables named table A and table B. Table B primary key is the foriegn key in the table A. for this how i need to write the hbm file and also how i need to insert the values into both the tables simultaneously by using only one object. (ie., how should i need to write the table A class file and table B class file.)
if any one explains me in the set by step procedure it will be easier for me to understand.
This is covered in the NH doc. The relationship you are talking is a <many-to-one/>, search for it here:
http://knol.google.com/k/fabio-maulo/nhibernate-chapter-5-basic-o-r-mapping/1nr4enxv3dpeq/8#
you will find some examples. In order to have the intellisense inside Visual Studio when you write the HBM files, you can copy these files
nhibernate-configuration.xsd
nhibernate-mapping.xsd
in the C:\Programme\Microsoft Visual Studio xxx\Xml\Schemas path.
In order to save simultaneously the referred entity you have to ensure to apply cascade="save-update" on the <many-to-one/> tag.
Related
I am not sure how to ask this question so please direct me in the right direction if I am not using the appropriate terminology, etc. but I can explain what I am currently doing. I would like to know if there is an easier way to update content in the database than the method I'm currently using.
(I'm using SQL Server 2008 BTW.)
I have a bunch of CSV files that I use to give to my client as a means to update content which gets imported into the DB (because the content is LARGE). The import works by running a python script that I wrote that makes use of a Jinja2 template that generates the SQL file needed to insert the CSV content into the database (if it is a from-scratch scenario). This is working fine.
Now when it comes to data migration (I need to migrate the data that exists in the DB to a new version thereof) I have a lot of manual work (I hand code it in the template, there is no SQL command or auto-generated code that I can run to do this for me) to do.
So lets say I have a list of Hospitals in a CSV file and I already have a set of hospitals in the database (which is imported from the previous version of the CSV file). I create a copy of the Hospitals table (without the data) and call it HospitalsTemp. The new CSV hospitals are inserted into the HospitalsTemp table (at least that part is generated via the template).
The Hospitals table now gets detached from all its foreign-keys and constraints. Now I go through all the tables surrounding the Hospitals (again manually!) and replace the hospitalId which pointed to the old hospitalId with the new hospitalId (as I can do a lookup from the Hospitals to the HospitalsTemp based on the hospital code to ensure that referential integrity is retained).
Then I delete the Hospitals table and rename the HospitalsTemp to Hospitals and put back the foreign-keys and constraints on the new Hospitals table.
I hope I explained it well enough for everyone to understand. I'm really hoping for a simpler way to do this.
How do you know which hospital becomes which, do the names stay the same? Is there an Id that stays the same?
Have you looked at SSIS, and the Slowly Changing Dimension component? You can use it to update existing rows and add new rows: http://blogs.msdn.com/b/karang/archive/2010/09/29/slowly-changing-dimension-using-ssis.aspx
Also SSIS would be a good tool for the import, as it handles reading CSV files well.
You could replace the current logic with simple SSIS package that's just a flat-file data source and the output of the SCD wizard by the sounds of it?
I have one excel file that I want to import into two different tables, tblUni and tblUser.
I have a third table which contains the id's from the other two tables:
tblUni_Students
Id
UniId
StudentId
What I need is when I import the excel data into the first two tables, for each record, the newly created ids to be inserted into the Uni_Students table also.
Using SSIS, I have managed to import the data into two sql destinations but cannot seem to then take the new ids from these destinations to then insert into the lookup table.
Can anyone advise please. Thanks.
It's a bit difficult to answer without knowing the target database or the structure of the data but speaking generally this would be much better done by adding the data into a "load" table. i.e. one who's sole reason is to temporarily hold data while you process it, you would then update the tblStudent, tblUni and tblUni_Student tables from the load area using SQL statements either via Procedure or via an Execute SQL Task component.
You'd it as an oledbcommand component, where the command is to insert values into the table. Then in the same component you'd output the generated identity. Assign the generated identity to a new column in the output, and now you have all your data plus the generated identity in the dataflow.
This will be processed one row at a time, so it will be slow. Personally I'd put it in a staging table and do it as Ciarán described.
I have a SQL Server view CyclesList on the table Cycle. Cycle table contains a few columns, and CyclesList view add some more data that can be computed on database level.
And now, I have a NHibernate mapping that points to CyclesList:
<class name="Cycle" table="CyclesList">
However, I would still like to work with Cycle class, and perform Create/Update operations , but I have to use stored procedure that will access Cycle table directly. Is there a way to achieve it in NHibernate? I would appriciate a sample mapping/links to resources with samples. Thanks
You find some information in the docs under "Native-Sql -> Custom SQL for create, update and delete". Basically, you need the "sql-insert", "sql-delete" and "sql-update" elements in the mapping file.
There is also an example on Ayendes blog.
I'm using Fluent NHibernate (and I'm a newbie). I have mapped a read-only table that already exists in the database (it's actually a view in the db). In addition, I have mapped new classes for which I want to create tables using SchemaExport.Create().
In my fluent mapping, I have specified "ReadOnly()" to mark the view as immutable. However, when I execute SchemaExport.Create(), it still tries to create the table so I get the error "There is already an object named 'vw_Existing'".
Is there a way to prevent NHibernate from trying to create that specific table?
I supposed I could export and modify the sql (SetOutputFile), but it would be nice to use SchemaExport.Create().
Thanks.
You're looking for
SchemaAction.None();
I've been writing a Library management Java app lately, and, up until now, the main Library database is stored in a .txt file which was later converted to ArrayList in Java for creating and editing the database and saving the alterations back to the .txt file again. A very primitive method indeed. Hence, having heard on SQL later on, I'm considering to port my preexisting .txt database to mySQL. Since I've absolutely no idea how SQL and specifically mySQL works, except for the fact that it can interact with Java code. Can you suggest me any books/websites to visit/buy? Will the book Head First with SQL ever help? especially when using Java code to interact with the SQL database? It should be mentioned that I'm already comfortable with using 3rd Party APIs.
View from 30,000 feet:
First, you'll need to figure out how to represent the text file data using the appropriate SQL tables and fields. Here is a good overview of the different SQL data types. If your data represents a single Library record, then you'll only need to create 1 table. This is definitely the simplest way to do it, as conversion will be able to work line-by-line. If the records contain a LOT of data duplication, the most appropriate approach is to create multiple tables so that your database doesn't duplicate data. You would then link these tables together using IDs.
When you've decided how to split up the data, you create a MySQL database, and within that database, you create the tables (a database is just something that holds multiple tables). Connecting to your MySQL server with the console and creating a database and tables is described in this MySQL tutorial.
Once you've got the database created, you'll need to write the code to access the database. The link from OMG Ponies shows how to use JDBC in the simplest way to connect to your database. You then use that connection to create Statement object, execute a query to insert, update, select or delete data. If you're selecting data, you get a ResultSet back and can view the data. Here's a tutorial for using JDBC to select and use data from a ResultSet.
Your first code should probably be a Java utility that reads the text file and inserts all the data into the database. Once you have the data in place, you'll be able to update the main program to read from the database instead of the file.
Know that the connection between a program and a SQL database is through a 'connection program'. You write an instruction in an SQL statement, say
Select * from Customer order by name;
and then set up to retrieve data one record at a time. Or in the other direction, you write
Insert into Customer (name, addr, ...) values (x, y, ...);
and either replace x, y, ... with actual values or bind them to the connection according to the interface.
With this understanding you should be able to read pretty much any book or JDBC API description and get started.