Yes, "IN" isn't supported by Ur/Web at the moment, and I would be glad
to see a PR adding support! It could probably be as simple as modeling
the second argument of "IN" as a regular Ur/Web list, processed
internally with a fold similar to what Simon wrote externally (but
generating "IN" syntax instead of a compound Boolean condition).
On 1/12/19 10:50 AM, Artyom Shalkhakov wrote:
Hi Simon,
сб, 12 янв. 2019 г. в 16:15, Simon Van Casteren <[email protected]>:
Hi,
Am I correct in thinking that the standard library/compiler doesn't support SQL
"IN" statements? It's something that I use a lot in my programs, and in psql
for example you can just do:
SELECT *
FROM uw_lesson_lessons
WHERE uw_id in (1, 2, 3)
Yes, it doesn't seem to be supported at the moment.
I made my own function to handle this, using a bunch of sql_or statements:
fun inlist
[a ::: Type]
[otherfields ::: {Type}]
[tablename :: Name]
[columnname :: Name]
[otherfields ~ [columnname = a]]
(_ : sql_injectable a)
(ids: list a)
: sql_exp ([tablename = [columnname = a] ++ otherfields]) ([]) ([]) bool
=
List.foldl
(fn id acc => (SQL {acc} OR {{tablename}}.{columnname} = {[id]}))
(WHERE {[False]})
ids
I'm not sure about the performance characteristics of this though. Anyway, just
wondering if it is already supported but I can't find it, or it's not supported
at all?
Well I think you should really file an issue for this on GitHub. I'd
like to work on it but it seems that it would require extending
Ur/Web's grammar, then adding some way to handle the right-hand side
of the operator -- which is an SQL tuple (right?), and we don't have
those in the syntax elsewhere except the INSERT clause handling. This
is a bit too much for my ability right now.
Other than that, I'm really in favor of adding it.
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