Hi Craig,
I went through the query chapter of the January 18 version of the JDO
spec and would like to propose a few changes to be added to describe
subqueries:
- section "14.3 Architecture: Query"
The subsection titled "Other elements in queries include:" should get a
new bullet about subqueries.
-section "14.6 Query Interface"
The subsection "Query element binding" should mention the 4 new methods
addSubquery to support subqueries.
- section "14.6.13 Single-string Query element binding"
I propose to mention subqueries in this section. Maybe after the
sentence "<filter> is the filter as in 14.6.2.", something like:
The filter in the single String form may include subqueries. A suquery
has the following structure:
select subquery-result-clause from subquery-from-clause where filter decls
The subquery-result-clause consists of an optional keyword distinct
followed by a single expression.
The subquery-from-clause may have one of two forms:
- A candidate class name followed by an optional alias definition
followed by an optional exclude subclasses
- A field access expression followed by an optional alias definition
An alias definition consists of an optional keyword as followed by an
identifier. This identifier may be used instead of this to access the
candidate instances of the subquery.
- section "14.10 Examples"
How about adding one or two subquery examples? We could use the TCK
subqueries as examples, e.g.
- Class NonCorrelatedSubqueries method runTestSubqueries01: select
employees who work more than the average of all employees:
SELECT FROM com.xyz.hr.Employee WHERE this.weeklyhours > (SELECT
AVG(e.weeklyhours) FROM com.xyz.hr.Employee e)
- Class CorrelatedSubqueriesWithParameters method runTestSubqueries01:
select employees who work more than the average of the employees in
their department having the same
manager:
SELECT FROM "com.xyz.hr.Employee WHERE this.weeklyhours > (SELECT
AVG(e.weeklyhours) FROM this.department.employees e WHERE e.manager ==
this.manager)
Regards Michael
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