[Hibernate-issues] [Hibernate-JIRA] Commented: (HB-117) Support for more SQL functions in SELECT

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The following comment has been added to this issue:

     Author: David Channon
    Created: Sun, 3 Aug 2003 9:05 AM
       Body:
The initial cut for this change has been completed. 
What I have done:
  * Moved the hard coded aggregate functions into the base Dialect.
  * Added the facility of other Dialects to add Dialect 
    specific functions.
    In my case I have change the Oracle9i Dialect by adding trunc,
    sysdate, and other functions
  * Modified the SelectParser to simplify parsing of aggregate
    functions. No longer have special cases for count or avg
    functions.
  * Added an interface and general class for suppling the return
    type of the function.
  * Added an extra test(s) to SQLFunctionTest

Given I have added extra functions to the Oracle dialect you can now
use extra select functions such as..

   select sysdate, trunc(s.value) from s as class simple

 
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View the issue:

  http://opensource.atlassian.com/projects/hibernate/secure/ViewIssue.jspa?key=HB-117


Here is an overview of the issue:
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        Key: HB-117
    Summary: Support for more SQL functions in SELECT
       Type: Improvement

     Status: In Progress
   Priority: Major

    Project: Hibernate2
 Components: 
             core

   Assignee: David Channon
   Reporter: Gavin King

    Created: Sun, 1 Jun 2003 7:58 PM
    Updated: Mon, 9 Jun 2003 6:44 AM

Description:
Currently, Hibernate supports exactly five (hardcoded) SQL functions in the HQL SELECT clause. They are the aggregate functions COUNT(), AVG(), SUM(), MIN(), MAX()

A number of users would like to be able to specify an arbitrary SQL function in the SELECT. The problem here is that we need to know the return type of the function to be able to read it from the result set.

I propose that the Dialect classes include a collection of mappings from function names to Hibernate types (eg. CURRENT_DATE -> Hibernate.DATE). That way, we can support the most commonly used SQL functions, and others can be easily added by users providing extensions to the Dialect.


So, we would like to allow:

SELECT CURRENT_DATE(), TRUNC(foo.amount), ......


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