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HOWTO: Create a UNIQUE constraint using NHibernate

I got an email question yesterday about how to create a UNIQUE contraint on a table using NHibernate.  After some research on the NHibernate Forum and digging through the NHibernate source code, I was able to find a solution.

(NOTE: my blog engine, .Text doesn't unfornately allow me to put html or xml directly in the text of a post so I'm putting element names in quotes.)

Usually, when you're mapping properties you only deal with the “property” element but “property” has an optional child element, “column” that lets you specify more detail for how NHibernate handles the column mapping.  One of the attributes is “unique-key” and it lets you define a named, unique grouping of properties/columns.  Set the unique-key attribute to the same value for all properties you want to group together and Voila! a UNIQUE constraint. 

Here's a sample class mapping with a UNIQUE constraint on FirstName and LastName. 

-Ben

 

 

 

posted @ Sunday, April 02, 2006 12:16 PM

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# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by DataSmithy at 7/19/2006 10:41 PM
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I guess the advantage to this is that it validates the unique key on the .NET side, and generate a .NET error instead of a SQL error if you try and insert a duplicate value?

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by koko at 8/27/2006 9:29 PM
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Regarding the unique-key attribute, I specified it in my class, however I can still succesfully save duplicates for that specified unique key.

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by Rich Cox at 9/27/2006 10:50 PM
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I just researched this today, the 'unique' attribute is only used when generating DDL from mapping files. It doesn't cause any enforcement of uniqueness in the poco, or NHibernate layers...

Rich C.

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by ביטוח רכב at 10/20/2006 8:58 AM
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I guess the advantage to this is that it validates the unique key on the .NET side, and generate a .NET error instead of a SQL error if you try and insert a duplicate value?

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by ביטוח רכב at 11/16/2008 4:14 AM
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Great mind thinking
We r with u

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by הכשרה מקצועית at 1/26/2009 10:58 AM
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very good article

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by בגדי תינוקות at 1/26/2009 11:07 AM
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love your writing

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by טיסות לתאילנד at 3/2/2009 7:30 AM
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i going to bookmark

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by טיסות לתאילנד at 3/22/2009 5:51 AM
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loved it

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by מכונות שטיפה at 3/22/2009 11:48 AM
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Great mind thinking
We r with u

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by בגדי תינוקות at 5/10/2009 1:31 PM
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loved it

# re: HOWTO: Create a UNIQUE constraint using NHibernate

Left by מדבקות קיר at 6/9/2009 6:18 AM
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LOVE IT

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