Re: relational tables and objects

Dm. Arapov wrote:
>Jan Hidders wrote
>> Dm. Arapove wrote:
>> >
>> >Result of this call will be object of class join_t_eq<TableA, TableB,
>> >list_of_columns_to_be_equal>.
>>
>> Interesting. Why is the list of columns in the type? And if I do
>> join(A,join(B,C)) will the result have the same type as join(join(A,B),C)
>> or not?
>
>Yes they will have the same type.

Which type will that be? Let's say A has colums a1 and a2, B has b1 and b2 and C has c1 and c2, and B and C are joined on b1 and c1 and A and B are joined on a1 and b2.

>List of columns let us tell compiler which of join use

What I meant was why is it a template variable and not simply an argument?

>>So can you statically type the set union?
>
>Pardon me, I do not understand the question.

If I call union(A,B) this should preferrably only be well typed if A and B have the same type. Is this decided at compile time?

• Jan Hidders