[odb-users] Query a many-to-many relationship

[dieter.govaerts at bricsys.com]

Hello Boris,

On Monday, 6 July, 2015 18:37, "Boris Kolpackov" <boris at codesynthesis.com> said:

> dieter.govaerts at bricsys.com <dieter.govaerts at bricsys.com> writes:
> 
>> I've been though all example projects (2.3.0) but I don't seem to find
>> an easy way to query objects based on a many-to-many relationship.
>>
>> Referring to the 'relationship' example project, how can I query all
>> employees working on project "Complex Hardware"?
> 
> That is actually not a to-many relationship, so you can use normal
> object queries:
> 
> typedef odb::query<employee> query;
> 
> db.query<employee> (query::employer->name == "Complex Hardware");
> 
> For real to-many relationships you would use a view. If you want
> to load the whole object, then you would use an object loading view
> (Section 10.2 in the ODB manual; available since 2.4.0).

I wanted to query employees based on the name of the _projects_ they work on,
not its employers name.

Object loading views seems indeed the key. I'll have to upgrade to 2.4.0 and
try again.

Thank you.

Dieter