How to get YEAR from a DATETIME using DATEPART in HQL

Question

I'm new user in StackOverflow, and I need a help in a HQL string..

In SQL my query is something like this..

SELECT DISTINCT DATEPART(yyyy, Moment) AS Year,
FROM PRODUCT_SOURCE

How can I convert this to HQL?

I've tried this, but didn't work..

query = "SELECT DISTINCT DATEPART(year, p.Moment) as Year, " + 
        "FROM Product_Source as p";

Answer 1

I am basing this on SQL2008 dialect so change as you see fit.

 
 
 
  
  public class MsSql2008ExtendedDialect : MsSql2008Dialect { public MsSql2008ExtendedDialect() { RegisterFunction("DATEPART_YEAR", new SQLFunctionTemplate(NHibernateUtil.DateTime, "datepart(year, ?1)")); } }
 
  

And to use you would use your HQL like this

 
 
 
  
  query = "SELECT DISTINCT DATEPART_YEAR(p.Moment) as Year, " + "FROM Product_Source as p";
 
  

Edit As Diego quite righly points out most of the functions in MSSQL server are already registered. For a full list see https://github.com/nhibernate/nhibernate-core/blob/master/src/NHibernate/Dialect/MsSql2000Dialect.cs

So just use:-

 query = "SELECT DISTINCT year(p.Moment) as Year, " + "FROM Product_Source as p"; 

Answer 2

The year function is already mapped internally, so:

SELECT DISTINCT year(p.Moment) as Year,
FROM Product_Source as p

This is registered by the MsSql2000Dialect (from which newer MSSQL dialects inherit).

Now, this assumes Product_Source is the name of your class, which is odd, as it doesn't follow the usual .NET conventions (you should drop the underscore)