I'm a bit studying join types and trying to make a visualisation of
relations among them. As a result I've created an ER diagram
describing relations among them and it can be found here
http://gplivna.blogspot.com/2008/01/...g-bit-sql.html
I've tried to find something like that using google however the best I
could get was textual description. I'm not mathematician and studied
set theory a bit 10 years ago in university and almost all have no
forgotten so maybe it has some problems from set theory viewpoint.
So question is - is it generally ok? If you know anything similar
please add link either here or in my blog post. All comments welcome!
Thanks!
Gints

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 3:04*am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Join is indded the most important operation in the RM. However. SQL
classification of joins is quite ad-hock and not particularly
illuminating. There are many more interesting joins around.

The "normal" natural join is something that can be described as set
intersection join. There are also set containment join (aka relational
division) and symmetrized form of set containment join -- set equality
join.

The other direction is comparing joins in Binary Relation algebras
with joins in RA. In Relation algebras join is not commutative and is
not a generalisation of set intersection.

On Jan 25, 11:04 am, Gints Plivna <gints.pli... (AT) gmail (DOT) com> wrote:
Having only looked at your breakdown briefly, I can't give you much
comment (although I thought your time-bomb discussion of natural joins
was entertaining). However, I would say that in general I view natural
joins, equi-joins, etc. as specializations of the generalized theta
join. I'd be interested if other's share this perspective.