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Re: many-to-many query question


On Oct 25, 2007, at 8:59 PM, Lachlan Deck wrote:

On 26/10/2007, at 12:47 PM, Chuck Hill wrote:

On Oct 25, 2007, at 6:29 PM, Lachlan Deck wrote:

On 26/10/2007, at 10:40 AM, James Cicenia wrote:

I have a many-to-many relationship as such:

Portfolio --->>MetricGroups--->>MetricItems<----project_item---- >Project

How I can create a query where

project can have ( Items(a) OR Items(b) ) AND (Items(c)) 

Something like this...

NSMutableArray itemsAQuals = new NSMutableArray();
String keyPathToA = "blah.blah";
for ( Item a : itemsA ) {
itemsAQuals.addObject( new EOKeyValueQualifier( keyPathToA, EOQualifier.QualifierOperatorContains, a ) );
}

etc...

EOQualifier q = new EOAndQualifier( new NSArray( new Object[] {
	new EOOrQualifier(new NSArray(new Object[] {
		new EOAndQualifier( itemsAQuals ),
		new EOAndQualifier( itemsBQuals )
	} ) ),
	new EOAndQualifier( itemsCQuals )
} ) );

That will work in memory, but EOQualifier.QualifierOperatorContains won't generate correct SQL for most databases.

News to me. Which databases do you think this affects? MySql is being used here...

That is a good question. I have not re-tested this for a while so I did so. Here is the code that I used to test this:

ec.lock();
Zone zone = Zone.zoneWithID(ec, new Long(100));
EOQualifier qual = new EOKeyValueQualifier( "zones", EOQualifier.QualifierOperatorContains, zone );
EOFetchSpecification fetchSpec = new EOFetchSpecification (OrderDistribution.ORDERDISTRIBUTION_ENTITY_NAME,
qual, null);
NSLog.out.appendln(ec.objectsWithFetchSpecification(fetchSpec));
ec.unlock();

FrontBase produces:
SELECT etc. etc.
FROM "OrderDistribution" t0, "OrderDistributionZoneX" T1, "PPZone" T2
WHERE T2."oid" like 100 AND t0."oid" = T1."oidOrderDistribution" AND T1."oidZone" = T2."oid"

Which fails with
Next exception:SQL State:00 subclass = " -- error code: 208 -- msg: Semantic error 208. Expression in LIKE is not of type CHARACTER.*


Then I tried MS SQL (the only other db that I have ready to go) produces:
SELECT etc. etc.
FROM OrderDistribution t0, OrderDistributionZoneX T1, PPZone T2
WHERE T2.oid = ? AND t0.oid = T1.oidOrderDistribution AND T1.oidZone = T2.oid" withBindings: 1:100(oid)>

Which is correct. So maybe this is mostly a bug with FrontBase. It used to work with FrontBase, once, long ago. I recall trying this on other database (some or all of Oracle, DB2, OpenBase IIRC) and it did not consistently work. For that reason, I stopped using it. It is something to be aware of if you plan to target other databases.


Chuck




Do you use one that this works on?

I've seen problems when not using 'contains' when crossing toMany boundaries rather than the opposite. I could paste various usages of QualifierOperatorContains <here> but are you suggesting that it your experience it doesn't work at all for db fetches or just across more complex relational boundaries as above?

with regards,
--

Lachlan Deck

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References: 
 >many-to-many query question (From: James Cicenia <email@hidden>)
 >Re: many-to-many query question (From: Lachlan Deck <email@hidden>)
 >Re: many-to-many query question (From: Chuck Hill <email@hidden>)
 >Re: many-to-many query question (From: Lachlan Deck <email@hidden>)



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