Hi Brenton,
Yes the OFFSET/LIMIT syntax differs from backend to backend. However
in some instances (like MySQL/PostgreSQL) they have ensured
compatability so that the same statement will run on several DBs
although the syntax might not be considered 'native'. For something
like Oracle there actually isnt a syntax for LIMIT so instead they do
something like
SELECT * FROM (
SELECT
ROW_NUMBER() OVER (ORDER BY key ASC) AS rownumber,
columns
FROM tablename
)
WHERE rownumber <= n
But as you can see it would be trivial to express this in terms of
ClojureQL:
(defn oracle-take
[tname limit]
(-> (table (str "(SELECT ROW_NUMBER() OVER (ORDER BY key ASC)"
" AS rownumber,columns"
" FROM " (to-tablename tname) ")"))
(select (where (<= :rownumber limit)))
(project ["*"])))
(to-sql (oracle-table :users 10))
["SELECT * FROM (SELECT ROW_NUMBER() OVER (ORDER BY key ASC) AS
rownumber,columns FROM users) WHERE (rownumber <= ?)" 10]
>From the outset it has been my ambition to make ClojureQL extremely
composable and as far as possible allow users to directly insert
strings into the query to allow for backend specific customization.
The entire design-plan of this customization is not yet thought out so
input is welcomed. To me, flexibility and leaving with the power to
the user is the key to wide adoption across various backends.
Lau
On Nov 24, 11:42 pm, Brenton <bashw...@gmail.com> wrote:
> > ClojureQL does not take the backend in to account. This is the one
> > feature from the old CQL that I didn't want to carry over because it
> > would be impossible for me to cater to all backends. If you hit
> > specific problems, let me know and I'll see what we can do.
>
> > We adhere to SQL92 and test everything on MySQL and Postgres. If
> > you're in a situation where thats not good enough, its always possible
> > to supply part of your expression as a string.
>
> Lau
>
> Off the top of my head, I know that the LIMIT syntax for SQL Server is
> totally different. A lot of the apps that I write end up getting
> deployed using Oracle and SQL Server. If you plan for CQL to be widely
> used I think you will need to take backends into account. You don't
> need to implement them all yourself, but you should provide a way so
> that others can implement them when they need to.
>
> Brenton
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