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kasei merged 9 commits into from
May 28, 2026
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Update Aggregate Projection Restrictions. #380

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Update Aggregate Projection Restrictions.
kasei May 18, 2026
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Update spec/index.html
kasei May 23, 2026
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kasei May 27, 2026
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kasei May 27, 2026
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kasei May 27, 2026
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kasei May 27, 2026
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Update Aggregate Projection Restrictions language based on PR feedback.
kasei May 27, 2026
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Update spec/index.html
kasei May 28, 2026
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25 changes: 16 additions & 9 deletions spec/index.html
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Expand Up @@ -2960,10 +2960,18 @@ <h3>HAVING</h3>
</section>
<section id="aggregateRestrictions">
<h3>Aggregate Projection Restrictions</h3>
<p>In a query level which uses aggregates, only expressions consisting of aggregates and
constants may be projected, with one exception. When <code>GROUP BY</code> is given with one
or more simple expressions consisting of just a variable, those variables may be projected
from the level.</p>
<p>In a query level which uses grouping (either by the explicit use of a <code>GROUP BY</code> clause
or through the use of aggregates in projection, <code>HAVING</code>, or <code>ORDER BY</code> clauses),
every occurrence of a variable that appears in projection or SELECT expressions of that query level
MUST satisfy one of the following conditions:</p>
Comment on lines +2963 to +2966

@TallTed TallTed May 29, 2026

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Suggested change
<p>In a query level which uses grouping (either by the explicit use of a <code>GROUP BY</code> clause
or through the use of aggregates in projection, <code>HAVING</code>, or <code>ORDER BY</code> clauses),
every occurrence of a variable that appears in projection or SELECT expressions of that query level
MUST satisfy one of the following conditions:</p>
<p>In a query level which uses grouping (either by the explicit use of a <code>GROUP BY</code> clause,
or by the use of an aggregate in projection, a <code>HAVING</code> clause, or an <code>ORDER BY</code> clause),
every occurrence of a variable that appears in a projection or a SELECT expression of that query level
MUST satisfy one of the following conditions:</p>

@kasei kasei May 29, 2026

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@TallTed – This has already been merged. A new PR is probably the best approach for this change.

@TallTed TallTed Jun 8, 2026

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moved to issue #386 and pr #387

<ul>
<li>the variable, <var>V</var>, appears as a named <code>GROUP BY</code> variable (with the corresponding <code>GROUP BY</code> expression consisting of just the variable <var>V</var>, or having the form <code>(expr AS <var>V</var>)</code>)</li>
<li>the variable appears as part of a sub-expression within the SELECT expression and this sub-expression is used as an argument to an aggregate (e.g., <code>MIN(?v)</code> or <code>AVG(?v+2)</code>)
</li>
<li>the variable is introduced by an earlier SELECT expression in the same SELECT clause</li>
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</ul>
<p>If such a variable occurrence does not satisfy one of these conditions, the query is syntactically invalid.</p>

<p>For example, the following query is legal as ?x is given as a <code>GROUP BY</code>
term.</p>
<pre class="query nohighlight">
Expand All @@ -2974,12 +2982,11 @@ <h3>Aggregate Projection Restrictions</h3>
?x :q ?z .
} GROUP BY ?x (STR(?z))
</pre>
<p>Note that it would not be legal to project <code>STR(?z)</code> as this is not a simple
variable expression. However, with <code>GROUP BY (STR(?z) AS ?strZ)</code> it would be
<p>Note that it would not be legal to project <code>STR(?z)</code> as this expression is neither a simple variable,
nor a named <code>GROUP BY</code> expression. However, with <code>GROUP BY ?x (STR(?z) AS ?strZ)</code> it would be
possible to project <code>?strZ</code>.</p>
<p>Other expressions, not using <code>GROUP BY</code> variables, or aggregates may have
non-deterministic values projected from their groups using the <code>SAMPLE</code>
aggregate.</p>
<p>Other expressions which use variables not satisfying the above conditions may be
projected from their groups using the <code>SAMPLE</code> aggregate.</p>
</section>
<section id="aggregateExample2">
<h3>Aggregate Example (with errors)</h3>
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