Re: How to do a "SELECT DISTINCT"
Re: How to do a "SELECT DISTINCT"
- Subject: Re: How to do a "SELECT DISTINCT"
- From: Chuck Hill <email@hidden>
- Date: Tue, 22 Mar 2005 13:49:56 -0800
I'm not sure that Sacha's suggestion is what you want. If you want to
get all of the rows that have a unique name in them, then EOF is not
going to be helpful. The reason is that EOF maps objects to some
external, persistent, representation. It is very, very concerned with
maintaining the connect of an object to its external representation.
If there are multiple rows with the same name, SELECT DISTINCT will
return the data from one of them, but which one is not known. So your
fetch, if it were possible, would be saying to EOF "get me some random
objects, but make sure they have unique names". It is just not built
for that. I can't even think of how to do this in SQL, return entire
rows where the values in column are unique, but its been a while since
I had to do things like that in SQL.
If you want a list of names to use in a lookup list, then you should
further normalize your data do that the unique names are held in their
own object / table.
Chuck
On Mar 22, 2005, at 1:23 PM, Sacha Mallais wrote:
On Mar 22, 2005, at 1:03 pm, Sébastien Gruhier wrote:
I would like to perform a "select distinct" on my database.
Actually I do a fecthSpecification like this
EOFetchSpecification fetchSpec = new EOFetchSpecification("Table",
new
EOKeyValueQualifier("attribute",
EOQualifier.QualifierOperatorEqual,
new Integer(1)),
null);
editingContext.objectsWithFetchSpecification(fetchSpec);
I get all elements from Table that have "attribute = 1". I would
like to add something like only with a distinct "name".
Any ideas?
RTFM:
http://developer.apple.com/documentation/WebObjects/Reference/API/com/
webobjects/eocontrol/
EOFetchSpecification.html#setUsesDistinct(boolean)
--
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