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

[<leg...@at...>]

The following comment has been added to this issue:

     Author: David Channon
    Created: Mon, 4 Aug 2003 3:55 AM
       Body:
While doing further testing I decided to expand the scope of the
functionality. All of the above plus below. NOTE: I have added
Dialect functions only to Oracle thus these examples only apply to
the Oracle Dialect (at the moment).

Extra since last comment.
* The parser can deal with no argument functions with and without 
  parenthesis. This was required for Oracle as its current date
  function is sysdate with no parenthesis and other databases use
  empty pair of parenthesis. For example.

  select s.name, sysdate, trunc(s.pay), round(s.pay) from s in class Simple

* Nesting of functions is now allowed. For example:

 select abs(round(s.pay)) from s in class Simple
 select trunc(round(sysdate)) from s in class Simple

It is very easy to add functions to your Dialect of choice. 
I have attached a patch(s).
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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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