Aggrieved about aggregation using SQL queries

[Colin Coates]

I am very surprised about needing to query for SubType is null in Aggregation relationships; surely it should either be 'Strong' or 'Weak'? Could this be a bug?

Code: [Select]

select Start_Object_ID from t_connector
where Connector_Type = 'Aggregation'
and SubType = 'Strong'
or SubType = 'Weak'
or SubType is null;

[Colin Coates]

Sorry, query should be:

Code: [Select]

select * from t_connector
where Connector_Type = 'Aggregation'
and (SubType = 'Strong'
or SubType = 'Weak'
or SubType is null);

[Geert Bellekens]

You shouldn't really be testing the subtype at all.

I usually only test DestIsAggregate or SourceIsAggregate. 1 => Aggregation, 2 => Composition

Code: [Select]

select * from t_connector c
where c.Connector_Type in ('Association', 'Aggregation')
and c.DestIsAggregate > 0 or c.SourceIsAggregate > 0
Geert

[Colin Coates]

Whilst I have no doubt your reasons are impeccable, I don't really get why testing the Subtype is such a bad thing (apart from the "is null" issue, of course)?

[Geert Bellekens]

Whilst I have no doubt your reasons are impeccable, I don't really get why testing the Subtype is such a bad thing (apart from the "is null" issue, of course)?

Mainly because I want to know about all compositions or aggregations, not just the the "Aggregation" variant, but also the Association.

And UML doesn't know subtype strong/weak. It knows about AggregationKind on both ends being shared (1 in EA) or composite (2 in EA)

So the subtype is completely redudant and derived information, and I'm pretty sure even EA itself doesn't really use that field (hence the null values in there)

Geert

[qwerty]

AFAIR the aggregation underwent some change in the UML spec. Hence it's likely heritage.

q.

[Colin Coates]

Thanks for your comprehensive (if slightly unsettling) replies, Gentlemen!