问题
I'm trying to get something similar to the SQL below via QueryOver:
SELECT
docs.*,
(SELECT TOP 1 eventDate from events WHERE id=docs.id
AND type=4 ORDER BY eventDate DESC) as eventDate
FROM documents as docs
WHERE doc.accountId = ...
I've got close with a projection, however I'm not sure how to get the entire documents table back. Documents has a one-to-many relationship with Events, I don't want to outer join as it will bring multiple results, and an inner join may not bring back a row:
var query = QueryOver<Document>
.Where(d => d.Account == account)
.SelectList(list => list
.Select(d => d)
.Select(d => d.Events.OrderByDescending(e => e.EventDate).FirstOrDefault(e => e.Type == 4))
)
.List<object[]>()
.Select(d => return new DocumentSummary(d[0],d[1]) etc.);
Is there an easier way of performing subqueries for columns? I'm reluctant to replace this with the property performing a query in its get
.
回答1:
After some research it looks like HQL (which QueryOver is converted into) does not support TOP inside subqueries.
My solution: create a view which includes the computed properties, and then mark these properties in the mappings files as insert="false"
and update="false"
来源:https://stackoverflow.com/questions/7133983/using-a-subquery-for-a-column-with-queryover