Hey Roman,
The issue that I see with `sqlingvo`, and the thing which I was trying to
solve for myself, is that it doesn't compose well. Unless I'm missing
something, you have to generate the entire query in the one `sql` form. To
me, this is a big restriction and was the number one thing I was trying to
fix with `clojure-sql`.
The basic sort of thing I want to be able to do is this:
(def users (-> (table :users) (project [:id :person :username])))
(def people (-> (table :people) (project [:id :first-name])))
(def combined-query (-> people
(rename {:id :person})
(join users)
(project [:username :first-name])))
So now in queries I can use `people`, `users` and `combined-query` in the
same way. The only difference in terms of how I can compose them is that
they expose different fields (`users` exposes [:id, :person, :username],
`people` exposes [:id :first-name], `combined-query` exposes [:username
:first-name]). In this example it's not completely obvious why this would
be beneficial, but it means that I can change `users`, for instance, to
also have a `(select '(= :deleted false)` in its definition and no other
code has to change. They will all join/query against the users where
`deleted` is false without any other modifications of code.
This freedom of composition is what you have in relational algebra, and
what I was trying to get in Clojure as well. All the naming of tables and
field aliases and everything is handled by the library, so you only have to
worry about constructing the queries. Unfortunately SQL provides a number
of operations outside of the relational algebra model (grouping, sorting,
take/drop), so they've been "tacked on" as a bit of an afterthought and
could probably use some improvement.
Looking at `sqlingvo` did show up a mistake that I made in how I was
dealing with sorts, though, so thanks for that! I think our libraries just
have fairly different concerns at the moment.
Carlo
On 5 July 2013 20:59, r0man <roman.sche...@burningswell.com> wrote:
> Hi Carlo,
>
> if you'are looking for generating more complex SQL there's also:
>
> https://github.com/r0man/sqlingvo
>
> Roman.
>
> On Wednesday, July 3, 2013 10:48:07 AM UTC+2, Carlo wrote:
>>
>> Hey guys!
>>
>> I've been working on a small library to make writing SQL queries a little
>> bit easier. It's along the same lines as ClojureQL, but takes a different
>> approach and compiles into quite different SQL in the end.
>>
>> At the moment it's quite immature, but it should be able to support any
>> queries which can be expressed in relational algebra. There will be some
>> SQL queries which can't be expressed in clojure-sql, but hopefully there
>> won't be too many of those. A greater limitation is that at the moment the
>> SQL generation is specific to the PostgresSQL database (although any
>> contributions for other databases are welcome!).
>>
>> Dependency vector: [clojure-sql "0.1.0"]
>> Repository:
>> https://bitbucket.org/czan/**clojure-sql<https://bitbucket.org/czan/clojure-sql>
>> Clojars link:
>> https://clojars.org/clojure-**sql<https://clojars.org/clojure-sql>
>>
>> Let me know what you think!
>>
>> Carlo
>>
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