Support for outer joins

[ghost]

Hi,

is there any discussion about supporting outer joins? i looked a lot in google and i couldn't find it. I know it's because of the non-nullable fields becoming automatically nullable because of the nature of the outer join.

Actually i don't know where to start from, but a previous discussion or notes would be helpful,

Andras

[m4dc4p]

I have not seen any discussion about supporting outer joins. I think you
would need to start by determining how outer joins are represented in the
relational calculus (if at all). You would then want to think about how the
type of the query is represented. For example, a left join between T1 and
T2 on the column c1, where c1 is a non-nullable integer column in both
tables, might look like:

Query (Rel (T1.c1 Int) ...) -> Query (Rel (T2.c1 Int) ...) -> Query (Rel
(T1.c1 Int) (T2.c1 (Maybe Int)) ...)

After figuring out the types, you'll need think about how the query gets
"compiled" into SQL, but the types are the most important part.

On Thu, Nov 15, 2012 at 6:26 AM, agyomrey [email protected] wrote:

Hi,

is there any discussion about supporting outer joins? i looked a lot in
google and i couldn't find it. I know it's because of the non-nullable
fields becoming automatically nullable because of the nature of the outer
join.

Actually i don't know where to start from, but a previous discussion or
notes would be helpful,

Andras

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