The **SchemaUpdate** object provides database schema updating, by apparently generating and executing a series of **SQL UPDATE** statements (as well as constraint statements) when it&#39;s `void Execute(bool script, bool doUpdate)`
 function is called.  The SchemaUpdate class is in the `NHibernate.Tool.hbm2ddl` namespace, which can be found in the Nhibernate.dll file.

SchemaUpdate is mentioned in chapter 15 of the nhibernate 1.0.2 toolset guide, [here][1] (section 15.1.5).

&quot;The NHibernate FAQ&quot; had (link now expired) a more complete example of how to use SchemaUpdate:

    [Test]
    public void Update_an_existing_database_schema()
    {
        _cfg = new Configuration();
        _cfg.Configure();
        _cfg.AddAssembly(Assembly.LoadFrom(&quot;DataLayer.dll&quot;));
        var update = new SchemaUpdate(_cfg);
        update.Execute(true, false);
    }



  [1]: http://users.telenet.be/christianr/a_nodig_samen/VBNet/NHibernate%20Reference.pdf
  [2]: http://nhibernate.hibernatingrhinos.com/14/create-and-update-database-schema
  [3]: http://www.markdavidrogers.com/oxitesample/Blog/schemaupdate-for-nhibernate

I&#39;m trying to write some C# code that calls a method from an unmanaged DLL.  The prototype for the function in the dll is:

    extern &quot;C&quot; __declspec(dllexport) char *foo(void);

In C#, I first used:

    [DllImport(_dllLocation)]
    public static extern string foo();

It seems to work on the surface, but I&#39;m getting memory corruption errors during runtime. I think I&#39;m pointing to memory that happens to be correct, but has already been freed.

I tried using a PInvoke code gen utility called &quot;P/Invoke Interop Assistant&quot;.  It gave me the output:

    [System.Runtime.InteropServices.DLLImportAttribute(_dllLocation, EntryPoint = &quot;foo&quot;)]
    public static extern System.IntPtr foo();

Is this correct? If so, how do I convert this IntPtr to a string in C#?

PInvoke for C function that returns char *

What is a satellite assembly, and when should they be used?

What is a satellite assembly?

I&#39;m trying to figure out how to use NHibernate configuration with mapping to update table schemas, rather than dropping and recreating them.

Currently I&#39;m using the `NHibernate.Tool.hbm2ddl.SchemaExport` obj with FluentNHibernate to generate the database schema for a mysql database.  While I can&#39;t say it&#39;s a huge problem, whenever I call `SchemaExport.Execute` on the database, it&#39;s going to drop all the tables and then recreate them.  

What would be way cooler is if I could just have it update the existing table structures retaining data where possible.  But I don&#39;t really want to use a commerical product, or a code generator, because I don&#39;t like code generation in general, and I don&#39;t need this enough that I would consider paying for it. So hopefully any answer would keep these caveats in mind.

How to update database table schemas with NHibernate schema generation?

I'm trying to figure out how to use NHibernate configuration with mapping to update table schemas, rather than dropping and recreating them.
Currently I'm using the <code>NHibernate.Tool.hbm2ddl.SchemaExport</code> obj with FluentNHibernate to generate the database schema for a mysql database. While I can't say it's a huge problem, whenever I call <code>SchemaExport.Execute</code> on the database, it's going to drop all the tables and then recreate them.
What would be way cooler is if I could just have it update the existing table structures retaining data where possible. But I don't really want to use a commerical product, or a code generator, because I don't like code generation in general, and I don't need this enough that I would consider paying for it. So hopefully any answer would keep these caveats in mind.

&gt; Possible duplicate
&gt; https://stackoverflow.com/questions/90871/debug-vs-release-in-net

What is the difference between Debug and Release in Visual Studio?

What is the difference between Debug and Release in Visual Studio?

I&#39;m getting the error when accessing a Stored Procedure in SQL Server

    Server Error in &#39;/&#39; Application.
    Procedure or function &#39;ColumnSeek&#39; expects parameter &#39;@template&#39;, which was not supplied. 

This is happening when I call a Stored Procedure with a parameter through .net&#39;s data connection to sql `(System.data.SqlClient)`, even though I am supplying the parameter. Here is my code.

    SqlConnection sqlConn = new SqlConnection(connPath);
    sqlConn.Open();
            
    //METADATA RETRIEVAL
    string sqlCommString = &quot;QCApp.dbo.ColumnSeek&quot;;
    SqlCommand metaDataComm = new SqlCommand(sqlCommString, sqlConn);
    metaDataComm.CommandType = CommandType.StoredProcedure;
    SqlParameter sp = metaDataComm.Parameters.Add(&quot;@template&quot;,SqlDbType.VarChar,50);
    sp.Value = Template;

    SqlDataReader metadr = metaDataComm.ExecuteReader();

And my Stored Procedure is:

       USE [QCApp]
       GO
       SET ANSI_NULLS ON
       GO
       SET QUOTED_IDENTIFIER ON
       GO

       ALTER PROCEDURE [dbo].[ColumnSeek] 
           @template varchar(50)
       AS
       EXEC(&#39;SELECT Column_Name, Data_Type 
       FROM [QCApp].[INFORMATION_SCHEMA].[COLUMNS] 
       WHERE TABLE_NAME = &#39; + @template);

I&#39;m trying to figure out what I&#39;m doing wrong here.

**Edit:** As it turns out, Template was null because I was getting its value from a parameter passed through the URL and I screwed up the url param passing (I was using `@` for and instead of `&amp;`)


Procedure expects parameter which was not supplied

Suppose I have a method that takes an object of some kind as an argument.  Now say that if this method is  passed a null argument, it&#39;s a fatal error and an exception should be thrown.  Is it worth it for me to code something like this (keeping in mind this is a trivial example):

    void someMethod(SomeClass x)
    {
        if (x == null){
            throw new ArgumentNullException(&quot;someMethod received a null argument!&quot;);
        }

        x.doSomething();
    }

Or is it safe for me to just rely on it throwing NullException when it calls x.doSomething()?

Secondly, suppose that someMethod is a constructor and x won&#39;t be used until another method is called.  Should I throw the exception immediately or wait until x is needed and throw the exception then?

Throwing ArgumentNullException

[Path.Combine][1] is handy, but is there a similar function in the .NET framework for [URLs][2]?

I&#39;m looking for syntax like this:

    Url.Combine(&quot;http://MyUrl.com/&quot;, &quot;/Images/Image.jpg&quot;)

which would return:

`&quot;http://MyUrl.com/Images/Image.jpg&quot;`

  [1]: https://msdn.microsoft.com/en-us/library/system.io.path.combine%28v=vs.110%29.aspx
  [2]: http://en.wikipedia.org/wiki/Uniform_resource_locator


Path.Combine for URLs?

How do I check to see if a column exists in a `SqlDataReader` object?  In my data access layer, I have create a method that builds the same object for multiple stored procedures calls.  One of the stored procedures has an additional column that is not used by the other stored procedures.  I want to modified the method to accommodate for every scenario.

My application is written in C#.

Check for column name in a SqlDataReader object

Question says it all really, the default is for it to map as a `string` but I need it to map as an `int`.

I&#39;m currently using `PersistenceModel` for setting my conventions if that makes any difference. Thanks in advance.

**Update**
Found that getting onto the latest version of the code from the trunk resolved my woes.

How do you map an enum as an int value with fluent NHibernate?

I&#39;m writing an integration test where I will be inserting a number of objects into a database and then checking to make sure whether my method retrieves those objects.

My connection to the database is through NHibernate...and my usual method of creating such a test would be to do the following:

    NHibernateSession.BeginTransaction();
    
    //use nhibernate to insert objects into database
    //retrieve objects via my method
    //verify actual objects returned are the same as those inserted
    
    NHibernateSession.RollbackTransaction();

However, I&#39;ve recently found out about [TransactionScope][1] which apparently can be used for this very purpose...

Some [example code I&#39;ve found][2] is as follows:

    public static int AddDepartmentWithEmployees(Department dept)
    {
    
        int res = 0;
    
        DepartmentAdapter deptAdapter = new DepartmentAdapter();
        EmployeeAdapter empAdapter = new EmployeeAdapter();
        using (TransactionScope txScope = new TransactionScope())
        {
    
            res += deptAdapter.Insert(dept.DepartmentName);
            //Custom method made to return Department ID 
            //after inserting the department &quot;Identity Column&quot;
            dept.DepartmentID = deptAdapter.GetInsertReturnValue();
            foreach(Employee emp in dept.Employees)
            {
    
                emp.EmployeeDeptID = dept.DepartmentID;
                res += empAdapter.Insert(emp.EmployeeName, emp.EmployeeDeptID);
    
            }
            txScope.Complete();
    
        }
        return res;
    
    }

I believe that if I don&#39;t include the line `txScope.Complete()` that the data inserted will be rolled back. But unfortunately I don&#39;t understand how that is possible... how does the `txScope` object keep a track of the `deptAdapter` and `empAdapter` objects and their transactions on the database.

I feel like I&#39;m missing a bit of information here...am I really able to replace my `BeginTransaction()` and `RollbackTransaction(`) calls by surrounding my code using `TransactionScope`?

If not, how then does `TransactionScope` work to roll back transactions?

  [1]: http://msdn.microsoft.com/en-us/library/system.transactions.transactionscope.aspx
  [2]: http://dotnetslackers.com/articles/ado_net/Managing_Transactions_using_TransactionScope.aspx

How does TransactionScope roll back transactions?

I have a mapping along the lines of this.

    &lt;hibernate-mapping xmlns=&quot;urn:nhibernate-mapping-2.2&quot; namespace=&quot;Model.Entities&quot; schema=&quot;etl&quot; assembly=&quot;Model&quot; default-lazy=&quot;false&quot;&gt;
      &lt;class name=&quot;Model.Entities.DataField, Model&quot; table=&quot;mdm_field&quot;&gt;
        &lt;id name=&quot;FieldId&quot; column=&quot;field_id&quot; type=&quot;int&quot;&gt;
          &lt;generator class=&quot;native&quot; /&gt;
        &lt;/id&gt;
        &lt;many-to-one name=&quot;KeyField&quot; class=&quot;Model.Entities.Key, Model&quot; column=&quot;field_id&quot; /&gt;
      &lt;/class&gt;
    &lt;/hibernate-mapping&gt;

Now in the database the field_id in the mdm_field table sometimes has a value that does not exist in the related key_field table, so it is basically broken referential integrity. Because of this when I load the entity I get an error &quot;No row with the given identifier exists&quot;. How do I configure the mapping to work with this situation so it will not die on this situation.



nHibernate, No row with the given identifier exists

How do I use the Inverse Attribute? If I am not mistaken, for one to many relationships the inverse attribute must be set to true. For many-to-many relationships, one of the entity class inverse attributes must be set to true and another set to false. 

Anyone can shed some lights on this?

Inverse Attribute in NHibernate

I have been trying to get to grips with Hibernate&#39;s inverse attribute, and it seems to be just one of those things that is conceptually difficult. 

The gist that I get is that when you have a parent entity (e.g. Parent) that has a collection of Child objects using a **one-to-many** mapping, setting inverse=true on the mapping tells Hibernate that &#39;the other side (the Child) has responsibility to update itself to maintain the foreign key reference in its table&#39;. 

Doing this appears to have 2 benefits when it comes to adding Children to the collection in your code, and then saving the Parent (with cascade-all set): [you save an unneccessary hit on the database][1] (because without inverse set, Hibernate thinks it has two places to update the FK relationship), and according to the official docs:

&gt;  If the &lt;key&gt; column of a
&gt; &lt;one-to-many&gt; association is declared
&gt; NOT NULL, NHibernate may cause
&gt; constraint violations when it creates
&gt; or updates the association. To prevent
&gt; this problem, you must use a
&gt; bidirectional association with the
&gt; many valued end (the set or bag)
&gt; marked as inverse=&quot;true&quot;.

This all seems to make sense so far. What I don&#39;t get is this: when would you **NOT** want to use inverse=true on a one-to-many relationship?

  [1]: http://nhprof.com/Learn/Alert?name=SuperfluousManyToOneUpdate

When to use inverse=false on NHibernate / Hibernate OneToMany relationships?

Anyone working on the Android (&#39;gPhone&#39;) have or know of a place where I can find a good ORM tool for it? The code is written in Java, and the database is SQLite. What I would like to find is a tool that given the object definition, can auto-generate the tables and the CRUD functions (that would be awesome), or, barring that, a tool that can take the table definition, the object definition, and auto-generate the CRUD functionality. The rub is that all of this must happen within the Android framework, which has its own conventions as to how database access works.

Any good ORM tools for Android development?

As a web developer looking to move from hand-coded PHP sites to framework-based sites, I have seen a lot of discussion about the advantages of one ORM over another. It seems to be useful for projects of a *certain (?)* size, and even more important for enterprise-level applications.

What does it give me as a developer? How will my code differ from the individual SELECT statements that I use now? How will it help with DB access and security? How does it find out about the DB schema and user credentials? 

**Edit:** *@duffymo pointed out what should have been obvious to me: ORM is only useful for OOP code. My code is not OO, so I haven&#39;t run into the problems that ORM solves.*

What are the advantages of using an ORM?

I need to store some data in a Django model. These data are not equal to all instances of the model.

At first I thought about subclassing the model, but I’m trying to keep the application flexible. If I use subclasses, I’ll need to create a whole class each time I need a new kind of object, and that’s no good. I’ll also end up with a lot of subclasses only to store a pair of extra fields.

I really feel that a dictionary would be the best approach, but there’s nothing in the Django documentation about storing a dictionary in a Django model (or I can’t find it).

Any clues?

How to store a dictionary on a Django Model?

If you are motivate to the &quot;pros&quot; of an ORM and why would you use an ORM to management/client, what are those reasons would be?

Try and keep one reason per answer so that we can see which one gets voted up as the best reason.

Why should you use an ORM?

It&#39;s a pretty open ended question.  I&#39;ll be starting out a new project and am looking at different ORMs to integrate with database access.

Do you have any favorites?
Are there any you would advise staying clear of?

What Java ORM do you prefer, and why?

I have a class called ReportRequest as:

    public class ReportRequest
    {
        Int32 templateId;
        List&lt;Int32&gt; entityIds;

        public virtual Int32? Id
        {
            get;
            set;
        }

        public virtual Int32 TemplateId
        {
            get { return templateId; }
            set { templateId = value; }
        }

        public virtual List&lt;Int32&gt; EntityIds
        {
            get { return entityIds; }
            set { entityIds = value; }
        }

        public ReportRequest(int templateId, List&lt;Int32&gt; entityIds)
        {
            this.TemplateId = templateId;
            this.EntityIds = entityIds;
        }
    }

It is mapped using Fluent Hibernate as:

    public class ReportRequestMap : ClassMap&lt;ReportRequest&gt;
    {
        public ReportRequestMap()
        {
            Id(x =&gt; x.Id).UnsavedValue(null).GeneratedBy.Native();
            Map(x =&gt; x.TemplateId).Not.Nullable();            
            HasMany(x =&gt; x.EntityIds).Table(&quot;ReportEntities&quot;).KeyColumn(&quot;ReportRequestId&quot;).Element(&quot;EntityId&quot;).AsBag().Cascade.AllDeleteOrphan();
        }
    }

Now, I create an object of this class as 

    ReportRequest objReportRequest = new ReportRequest(2, new List&lt;int&gt;() { 11, 12, 15 });

and try to Save the object in database using 

    session.Save(objReportRequest);

I get the following error:
*&quot;Unable to cast object of type &#39;NHibernate.Collection.Generic.PersistentGenericBag`1[System.Int32]&#39; to type &#39;System.Collections.Generic.List`1[System.Int32]&#39;.*&quot;


I am not sure if I have mapped the property EntityIds correctly.
Please guide.

Thank you!

Unable to cast object of type NHibernate.Collection.Generic.PersistentGenericBag to List

How to configure Fluent NHibernate to output queries to Trace or Debug instead of Console?
I&#39;m using `MsSqlConfiguration.MsSql2008.ShowSql()` but it has no parameters and I can&#39;t find anything on Google.


How to configure Fluent NHibernate to output queries to Trace or Debug instead of Console?

I know how to log the SQL to log4net/NLog/trace window at runtime with the `show_sql` configuration option.

What I&#39;m looking for is a way to give a `Query&lt;T&gt;()` to NHibernate retrieve the generated SQL.

I&#39;ve looked through the Persister class, the Drivers, different Interceptors and Events. There are so many places to look, even narrowing down my search would be of great help.

How can I have NHibernate only generate the SQL without executing it?

Are there any good tools for visualising a pre-existing database schema? I&#39;m using MySQL if it matters.

I&#39;m currently using MySQL Workbench to process an SQL create script dump, but it&#39;s clunky, slow and a manual process to drag all the tables about (which would be okay if it wasn&#39;t so slow).

Good tool to visualise database schema?

I have the following Rails migration which works perfectly (irrelevant pieces removed):

    create_table :comments do |t|
      t.text :body
      t.references :post
    end

Now I&#39;d like to add an `author` column to my `comments` table (which is the userid of a user), but I have no idea how to do it (I&#39;m tempted to just write the MySql-specific syntax using an `execute`). 

I&#39;ve been looking at add_column [here][1] which doesn&#39;t mention `references`. I&#39;ve actually found [TableDefinition#references][2] but I have no idea how to use it with an `add_column` statement.

Is this possible? Also, is it true that, for MySql, the &quot;references&quot; functionality does not actually establish relationships between the tables?



  [1]: http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#M001658
  [2]: http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html#M001737

add_column for references (Rails)

I&#39;m no beginner to using SQL databases, and in particular SQL Server.  However, I&#39;ve been primarily a SQL 2000 guy and I&#39;ve always been confused by schemas in 2005+.  Yes, I know the basic definition of a schema, but what are they really used for in a typical SQL Server deployment?

I&#39;ve always just used the default schema.  Why would I want to create specialized schemas?  Why would I assign any of the built-in schemas?

EDIT: To clarify, I guess I&#39;m looking for the benefits of schemas.  If you&#39;re only going to use it as a security scheme, it seems like database roles already filled that.. er.. um.. role.  And using it a as a namespace specifier seems to have been something you could have done with ownership (dbo versus user, etc..).

I guess what I&#39;m getting at is, what do Schemas do that you couldn&#39;t do with owners and roles?  What are their specifc benefits?

What good are SQL Server schemas?

What are the differences between PRIMARY, UNIQUE, INDEX and FULLTEXT when creating MySQL tables?

How would I use them?

Differences between INDEX, PRIMARY, UNIQUE, FULLTEXT in MySQL?

I want to write a calendar application. It is really recurring items that throw a wrench in the works for the DB schema. I would love some input on how to organize this.

What if a user creates an event, and inputs that it repeats everyone Monday, forever? How could I store all that in the database? I can&#39;t create infinite events. Do I simply put a table in there that holds the relevant info so I can calculate where all the events go? If so, I would have to calculate them every time the user views a new part of the calendar. What if they page through the months, but they have a ton of recurring items?

Also, the schema needs to handle when a user clicks an item and says &quot;Edit this one in the sequence&quot; not all items in the sequence. Do I then split the one item off of the sequence?

**Update 1**

I have not looked at iCal at all. To be clear, I think saving the info that allows you to calculate the recurring items, and splitting off any that differ from the sequence is a great way to store it to be able to transfer it. But I think that in an application, this would be too slow, to do the date math all over the place.

Content Type	Original Author	Original Content on Stackoverflow
Question	Mark Rogers	View Question on Stackoverflow
Solution 1 - .Net	Mark Rogers	View Answer on Stackoverflow

How to update database table schemas with NHibernate schema generation?

.Net Problem Overview

.Net Solutions

Solution 1 - .Net

What is a satellite assembly?

PInvoke for C function that returns char *

Attributions