Hi Matthew, hi Christiaan,
I agree that the candidateCollectionExpression description is a bit
cryptic.
Do you have an idea for a better description? The reason to include
something like "tokens from this query" is that we have to define the
scope for identifiers used in the candidateCollectionExpression. So in
"this.department.employees" this denotes the candidate instance of the
outer query and NOT of the subquery.
Boy, it's been a long time since I thought about subqueries. Can we
also provide single-string versions of the examples? That would be
helpful.
Do you mean add single string JDOQL of the examples to the spec or
provide them for this email discussion? I agree it would be useful to
add them to the spec. If you are just interested for right now:
- employees who work more than the average of all employees
SELECT FROM Employee WHERE this.weeklyhours > (SELECT AVG(e.weeklyhours)
FROM Employee e)
- employees who work more than the average of their department employees
SELECT FROM Employee WHERE this.weeklyhours > (SELECT AVG(e.weeklyhours)
FROM this.department.employees e)
- employees who work more than the average of the employees in their
department having the same manager:
SELECT FROM Employee WHERE this.weeklyhours >
(SELECT AVG(e.weeklyhours) FROM Employee e WHERE e.manager ==
this.manager)
Christiaan,
yes, I think the query code you added to your email returns the same result.
Regards Michael
-matthew
On Oct 25, 2007, at 5:07 AM, Christiaan wrote:
Hi Craig,
the examples are very informative. I must say that I find the
description
for candidateCollectionExpression
"The candidateCollectionExpression is the expression using tokens from
this query that represent the candidates over which the subquery is
evaluated. "
a little bit cryptic (I actually find the paramater name more
descriptive
than the description). Especially "tokens from this query" (is tokens a
common word for this and may be it should be stressed that this query
is the
outer query?) and "over which the subquery is evaluated", but may be
this is
needed for the spec.
Anyway, do I understand it correctly that it is the same as:
....
sub.setFilter(":departmentEmployees.contains(this)");
Query q = pm.newQuery(Employee.class);
q.setFilter("this.weeklyHours > averageWeeklyhours");
q.addSubquery(sub, "double averageWeeklyhours", null,
"this.department.employees");
kind regards,
Christiaan
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