Dave,
By the way, the example you gave doesn't work under Oracle.
You'd have to use
select * from artist ORDER BY case when artist_name = 'Tom' then 1
else 2 end DESC;
Not sure if that's relevant your environment.
And just to clarify, when I said "I don't think it supports
expressions, only columns, in the ordering.", I meant that I don't
think Cayenne supports expressions in the ordering.
On Tue, Mar 16, 2010 at 2:11 PM, Mike Kienenberger <mkienen..mail.com> wrote:
> Michael,
>
> I think you're misunderstanding him.
>
> He's telling you exactly what he wants.
>
> SELECT * FROM artist ORDER BY artist_name = 'Tom' DESC;
>
> http://www.informit.com/articles/article.aspx?p=339935&seqNum=2
>
> http://searchoracle.techtarget.com/answer/CASE-expressions-in-the-ORDER-BY-clause
>
> I'm not sure if Cayenne supports it. I've never seen that notation
> before. I don't think it supports expressions, only columns, in the
> ordering.
>
> I'd say it's a pretty database-specific function (but maybe I'm wrong).
>
>
> On Tue, Mar 16, 2010 at 1:53 PM, Michael Gentry <mgentr..asslight.net> wrote:
>> Hi Dave,
>>
>> You are close, but not quite there. The ordering only applies to a
>> column (artistName), but you are giving it a qualifier/expression
>> (artistName = 'Tom'). You need to create the expression separately
>> (multiple ways to do that, but I'll show one):
>>
>> Expression expression = ExpressionFactory.match("artistName", "Tom");
>> SelectQuery query = new SelectQuery(Artist.class, expression);
>> query.addOrdering("artistName", SortOrder.DESCENDING);
>> context.performQuery(query);
>>
>> You might want to look at:
>>
>> http://cayenne.apache.org/doc30/parameterized-queries.html
>> http://cayenne.apache.org/doc30/api/org/apache/cayenne/exp/ExpressionFactory.html
>> http://cayenne.apache.org/doc30/api/org/apache/cayenne/exp/Expression.html
>>
>> Expressions are where you do the WHERE clause. Also, instead of
>> hardcode "artistName", you probably have Artist.ARTIST_NAME_PROPERTY
>> available as a constant which is safer to use.
>>
>> mrg
>>
>>
>> On Tue, Mar 16, 2010 at 1:33 PM, Dave Dombrosky <dombr..mail.com> wrote:
>>> Yes I'm using Cayenne 3. I'm not sure if I stated the problem in
>>> enough detail, because it seems like you guys are confused. Or maybe
>>> I just don't understand how to use what you are telling me about.
>>>
>>> Maybe it would be better if I was helped with a full example. Using
>>> the Artist class from Cayenne's test schema, how would I go about
>>> creating a SelectQuery to order all artists with the name "Tom" first?
>>> Basically to generate a query similar to this:
>>>
>>> SELECT * FROM artist ORDER BY artist_name = 'Tom' DESC;
>>>
>>> Would it be like this?
>>>
>>> SelectQuery query = new SelectQuery(Artist.class);
>>> query.addOrdering("artistName = 'Tom'", SortOrder.DESCENDING);
>>> context.performQuery(query);
>>>
>>> Because that still gets the error Unsupported ordering expression:
>>> artistName = 'Tom'.
>>>
>>> Am I doing something wrong, or is this impossible with a SelectQuery?
>>> I'd rather not use SQLTemplate if I can avoid it.
>>>
>>> -Dave
>>>
>>> On Tue, Mar 16, 2010 at 8:39 AM, Michael Gentry <mgentr..asslight.net> wrote:
>>>> Hi Dave,
>>>>
>>>> Since you are seeing deprecation warnings I'm assuming you are using
>>>> Cayenne 3? If so, you should use:
>>>>
>>>> addOrdering(Ordering ordering) or
>>>> addOrdering(String sortPathSpec, SortOrder order)
>>>>
>>>> These are defined for your SelectQuery object. Of course, if you are
>>>> using the first of those methods, you'll have to create your own
>>>> Ordering object first. The second creates one for you behind the
>>>> scenes.
>>>>
>>>> Let me know if you need additional pointers!
>>>>
>>>> mrg
>>>>
>>>>
>>>> On Tue, Mar 16, 2010 at 1:11 AM, Dave Dombrosky <dombr..mail.com> wrote:
>>>>> Is there any way to use sort expressions in a query? Something like
>>>>> "ORDER BY column = id"? I get the error "Unsupported ordering
>>>>> expression" when trying to execute a query with this in it.
>>>>>
>>>>> Also, it looks like I might be able to do this using in-memory
>>>>> sorting, but the Ordering(Expression sortExpression, ...) methods are
>>>>> deprecated. So what's the preferred way to sort on expressions in
>>>>> Cayenne?
>>>>>
>>>>> -Dave
>>>>>
>>>>
>>>
>>
>
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