Minor comment tweak about aggr()

Duke-GCB · Nov 7, 2023 · fe64703 · fe64703
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Showing 2 changed files with 3 additions and 3 deletions.
diff --git a/Lesson-04.qmd b/Lesson-04.qmd
@@ -540,7 +540,7 @@ GROUP BY i.Name, c.Name, c.Semester;
   - If neither, the value is from a randomly chosen member of the group.
 ```{sql, label=selectG1.1}
 SELECT i.Name AS Instructor, c.Name AS Course,
-       MAX(c.Semester) AS Semester, -- values are the same in a group; AGGR() ensures it's non-NULL
+       MAX(c.Semester) AS LastSemester, -- choose one non-NULL value from group
        COUNT(l.Name) AS '#Lessons'
 FROM Lesson AS l INNER JOIN Course AS c USING (Course_OID)
      RIGHT OUTER JOIN Instructor AS i USING (Instructor_OID)

diff --git a/pub/Lesson-04.html b/pub/Lesson-04.html
@@ -1491,7 +1491,7 @@ <h2>Grouping vs aggregating</h2>
 </ul>
 <div class="cell">
 <div class="sourceCode cell-code" id="cb46"><pre class="sourceCode numberSource sql number-lines code-with-copy"><code class="sourceCode sql"><span id="cb46-1"><a href="#cb46-1"></a><span class="kw">SELECT</span> i.Name <span class="kw">AS</span> Instructor, c.Name <span class="kw">AS</span> Course,</span>
-<span id="cb46-2"><a href="#cb46-2"></a>       <span class="fu">MAX</span>(c.Semester) <span class="kw">AS</span> Semester, <span class="co">-- values are the same in a group; AGGR() ensures it's non-NULL</span></span>
+<span id="cb46-2"><a href="#cb46-2"></a>       <span class="fu">MAX</span>(c.Semester) <span class="kw">AS</span> LastSemester, <span class="co">-- choose one non-NULL value from group</span></span>
 <span id="cb46-3"><a href="#cb46-3"></a>       <span class="fu">COUNT</span>(l.Name) <span class="kw">AS</span> <span class="st">'#Lessons'</span></span>
 <span id="cb46-4"><a href="#cb46-4"></a><span class="kw">FROM</span> Lesson <span class="kw">AS</span> l <span class="kw">INNER</span> <span class="kw">JOIN</span> Course <span class="kw">AS</span> c <span class="kw">USING</span> (Course_OID)</span>
 <span id="cb46-5"><a href="#cb46-5"></a>     <span class="kw">RIGHT</span> <span class="kw">OUTER</span> <span class="kw">JOIN</span> Instructor <span class="kw">AS</span> i <span class="kw">USING</span> (Instructor_OID)</span>
@@ -1503,7 +1503,7 @@ <h2>Grouping vs aggregating</h2>
 <tr class="header">
 <th style="text-align: left;">Instructor</th>
 <th style="text-align: left;">Course</th>
-<th style="text-align: left;">Semester</th>
+<th style="text-align: left;">LastSemester</th>
 <th style="text-align: right;">#Lessons</th>
 </tr>
 </thead>